The rogue has the best suite of character options for surviving the dungeon environment, including the ability to deal with traps and locks, skill at skulking about and advantages when striking from concealment. However, all the standard classes in the Player’s Handbook have abilities or strengths that are useful in a dungeon.
The following entries discuss choices you can make during character creation to improve your dungeoneering party. Each standard class entry also contains one or more alternative class features (introduced in Player’s Handbook II) to customize your character to the dungeon environment.
Your purpose in the dungeon is to fight, plain and simple. With your fast movement and melee prowess, you can reach trouble before it can get to your comrades. In close quarters, where tactical movement is important, Combat Reflexes can be advantageous. If you set up a blocking position in a 10-foot-wide hallway, no enemy can get past you easily. As always, Power Attack and Cleave are your friends.
Your uncanny dodge and trap sense abilities help you avoid surprise dangers, and damage reduction lets you endure more blows than most. Consequently, a party stuck without a rogue (or similar character) might depend on you to take care of traps — simply because you’ll get hurt less if you fail.
When the party is faced with obstacles, your high Strength allows you to move aside heavy objects, break down doors, and so forth. You can use Power Attack to help bust through inanimate objects more quickly. If you need an extra edge to accomplish such a task (especially if you’re in a hurry), it might even be worth expending a use of your rage to get the job done.
You have a knack for avoiding and disabling traps. Your keen instincts help you avoid danger, while your great strength enables you to disrupt dangerous devices.
Level: 3rd.
Replaces: If you select this alternative class feature, you do not gain the trap sense ability.
Benefit: Beginning at 3rd level, you gain trapfinding, except that you can use Survival instead of Search to locate traps. However, you take a -5 penalty on such checks because of your comparative unfamiliarity with the mechanisms and triggers involved.
Once you find a mechanical trap, you can attempt to disarm it by making an attack roll. You succeed if the result exceeds the Disable Device DC of that trap. Only traps with moving mechanisms or gears (such as shifting floor panels, dropping portcullis gates or arrow traps) can be disarmed in this manner; simple pitfalls and most magic traps have no mechanism to be so disrupted. You must be able to reach the trap with a melee attack to make a disarm attempt. If you fail to disarm the trap, you automatically spring it.
You are the expert at solving peculiar problems. Bardic Knowledge can give you information about the dungeon’s purpose or origin as a whole, the secret answer to an ancient riddle, or the name and powers of a magic item. If the party gets stuck, give bardic knowledge a try. The legend lore spell can supplement this ability.
Your bardic music has many useful functions, so you shouldn’t waste it on situations that aren’t truly dangerous. Don’t underestimate the inspire competence ability, though; it improves crucial skill checks, especially Disable Device and Climb, when poor rolls can mean serious trouble.
For your spell selections, focus on utility spells and those that mislead opponents. Light, know direction, animate rope, detect secret doors, gaseous form, dimension door, freedom of movement, shadow walk and find the path make navigation and movement smooth. Illusion spells, even simple ones such as ghost sound, can trick enemies who are unaware of your presence. Even your cantrips have wide utility: Detect magic can sort the treasure hoard, mage hand can grab a set of keys from a hook or drop a rock on a trap’s trigger plate, mending can fix a damaged coil of rope, and open/close can crack a door or trapped chest from a safe distance. Don’t skimp on your cure spells — you’ll need them.
Bardic music serves many purposes, aiding your allies or manipulating your enemies. You have refined your performance of another group of bardic songs, full of lost knowledge, obscure lore and relevant anecdotes. These lore songs inspire you to come up with new solutions to difficult problems.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain the bardic knowledge ability.
Benefit: Once per day, as an immediate action, you can gain a +4 insight bonus on a single attack, check or save. You gain one additional daily use of this ability at every odd-numbered bard level (3rd, 5th and so on).
You use your bardic music to create background noise consistent with your adventuring environment, shielding the sounds made by yourself and your adventuring party as you move through dangerous areas.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain the countersong bardic music ability.
Benefit: Mimicking song is a spell-like ability that requires you to have 3 or more ranks in a Perform skill. Using mimicking song counts as one of your daily uses of bardic music. You grant a +2 bonus on the Move Silently check of all allies within 30 feet (including yourself). This bonus increases by 2 for every five bard levels you have (to a maximum bonus of +10 at 20th level). This effect lasts as long as you continue performing.
In the dungeon, as elsewhere, your main function is to heal and protect. Your healing spells make you one of the most essential members of a dungeoneering party. Your defensive spells also keep your party out of danger. Putting ranks in the Heal skill can improve your ability to salve your companions’ wounds, as can the Sacred Healing and Sacred Purification feats. And of course, you are the party’s bastion against undead attack.
Choose domains that play to your strengths (such as Healing or Protection) or that overcome dungeon difficulties. The Travel domain can negate obstacles, and the Sun domain gives you some extra offensive magic and more power to face undead-infested dungeons.
You are also a competent melee combatant who can support the fighter or barbarian in your party. You might instead choose to reinforce this role, enhancing your fighting ability with combat-focused feats such as Weapon Focus or Divine Armour.
When you or your teammates lose your strength in the middle of a dungeon, you can’t always “call it a day” and rest. You can restore the party’s hit points by trading spells for healing magic, but other setbacks besides physical injury might impede your progress: insidious disease, vermin poison or noxious fumes. By focusing your divine purpose, you can restore your party’s lost abilities.
Level: 3rd.
Replaces: If you select this alternative class feature, you sacrifice one of your domain granted powers.
Benefit: At 3rd level, select one of your chosen cleric domains. You can still select and cast spells from that domain list, but you no longer can use the domain’s granted power. Instead, you gain the ability to spontaneously cast lesser restoration, restoration or greater restoration by sacrificing a prepared spell of the same level.
For example, Jozan is 3rd level and selects this alternate class feature. He had chosen the Healing and Protection domains at 1st level. He gives up the Healing domain granted power. He no longer casts healing spells at +1 caster level, but he can sacrifice a prepared 2nd-level spell to spontaneously cast lesser restoration. At 7th level, he’ll be able to sacrifice a 4th-level spell to cast restoration and at 13th level, a 7th-level spell to cast greater restoration.
Special: When spontaneously casting a restoration spell, you must still expend the required components.
Like the cleric, your purpose in the dungeon is to heal and support. Your nature-based abilities that depend on vegetation or being outdoors won’t help here, so focus on healing and enhancement spells such as barkskin, bull’s strength and greater magic fang (which works either on yourself in wild shape or on your animal companion). Spells that facilitate dungeon movement are worthwhile, including spider climb, warp wood, air walk, control water and freedom of movement, and offensive spells such as call lightning can be powerful even in close quarters underground.
At low levels, bypassing obstacles can be difficult. You can command an animal companion or creature summoned with a summon nature’s ally spell (assuming you can communicate with it) to perform a trick that will assist you. For example, a badger could burrow under a door, an eagle could carry a grappling hook to a high ledge, or a monkey could crawl through a narrow passage and lift a latch. By taking a wild shape, especially the elemental forms available to you at higher levels, you can navigate unusual terrain yourself and overcome obstacles the others cannot. Make sure to select the Natural Spell feat so you can use your magic while in wild shape.
You are a child of the underworld. While other druids dwell in lush forests and rolling fields, you tend to the mushroom tangles and lichen beds that lie beneath their feet.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain any of the following abilities: wild empathy at 1st level, woodland stride at 2nd level and resist nature’s lure at 4th level.
Benefit: At 1st level, you gain vermin empathy. This ability functions just like wild empathy, except that you can improve the attitude of vermin instead of animals, even though vermin are usually unintelligent.
At 2nd level, you gain the ability to move over stone, rock and earthen debris at your full speed without taking damage or suffering any other impairment. This ability functions only with natural surfaces. Magically altered surfaces, such as those created by soften earth and stone or spike stones, affect you normally.
At 4th level, you gain resistance to the powers of creatures most abhorrent to nature. You gain a +4 bonus on saving throws against the spell-like abilities of aberrations.
Your role in the dungeon is to fight strategically, protecting the weaker members of the party by holding off enemies. Ranged attacks are certainly possible in larger chambers, but your greatest strength is holding the line in melee. Focus your feats on those that enhance melee combat in tight spaces where movement is limited, such as Combat Reflexes, Cleave and Great Cleave, or Whirlwind Attack. Setting up tactical “pinch points”, as mentioned in the barbarian’s entry above, will let you deliver more pain than usual. The Vexing Flanker feat makes a flanking position even more deadly against enemies. If you’re worried about being caught in the dark, Blind-Fight can be useful.
Your Strength-based skills (Climb and Jump) are vital in the dungeon, allowing you to cross or exploit obstructing terrain. Unless you specialize in light armour and Dexterity-based combat, you’ll need maximum ranks to make up for your armour check penalty.
Aside from these considerations, your function isn’t much different from that in other situations. A blade is a blade in the dungeon or in the wilderness.
Survival in a dungeon requires more than skill at arms and a stout shield. Traps, hazards, falling portcullises and other threats can pose as much danger as an enraged troll. But you cannot help your impetuous nature. When others might move ahead cautiously and search for traps and other hidden dangers, you charge forward, ignoring the traps you set off and splintering doors and obstacles.
Level: 2nd.
Replaces: If you select this alternative class feature, you do not gain the fighter bonus feats at 2nd level and at 6th level.
Benefit: You excel at overwhelming traps, smashing through doors, and pushing aside your enemies. At 2nd level, you gain a +2 competence bonus on saves and to your Armour Class when attacked by traps. You also gain a +5 bonus on Strength checks to break a door, wall, or similar obstacle.
In addition, you gain a special benefit when making a bull rush. If you force an opponent to move into a wall or other solid object, he stops as normal. However, your momentum crushes him against it, dealing an amount of bludgeoning damage equal to 4d6 points + twice your Strength bonus (if any).
At 6th level, the bonuses when dealing with traps increase to +4, and the bonus on Strength checks to break objects increases to +10. The damage you deal when bull rushing an opponent into a wall increases to 8d6 points + three times your Strength bonus.
You are the party member most able to bypass dungeon obstacles, and you also provide combat support. Your varied class skills, substantial skill points, and lack of reliance on armour make you ideally suited to focusing on essential dungeoneering skills. Climb, Hide, Jump, Listen, Move Silently, Spot and Tumble are all good choices; depending on your ability scores, either dominate in one area or select a balanced array.
In combat, use your great mobility to set up flanking positions for other characters (especially the rogue). The Tumble skill can protect you from attacks of opportunity and allow you to move about the battlefield safely. The Acrobatic Strike feat makes tumbling even more worthwhile. For your bonus feats, Combat Reflexes and Improved Trip are useful selections: Knock foes prone, then slam them as they try to rise or crawl away.
Your other class features have broad utility in the dungeon, especially slow fall and immunity to disease and poison. At higher levels, the abundant step ability lets you bypass most obstacles with ease.
While most monks gain a fluid grace that allows them to move with astounding speed, you have learned how to focus your energy and expel it in one quick burst.
Level: 3rd.
Replaces: If you select this alternative class feature, your fast movement ability is reduced. You gain a +10-foot enhancement bonus to speed at 12th level and another +10-foot bonus at 18th level.
Benefit: At 3rd level, you can make a standing long jump with ease. The check DCs for your long jumps do not require a 20-foot running start and do not double when you leap from a standing position. At 6th level, you apply this skill to high jumps. The check DCs for your high jumps do not double when you leap from a standing position. You lose these benefits when wearing armour (even light armour) or when carrying a medium or heavy load.
You have the uncanny ability to travel along vertical surfaces for a short time.
Level: 4th.
Replaces: If you select this alternative class feature, you do not gain the slow fall ability.
Benefit: Beginning at 4th level, as a move action, you can run up or down a vertical surface a total distance of 20 feet without making a Climb check. You add 10 feet to this distance at 6th level and every two levels thereafter, up to your maximum speed. You can use this ability only once per round (so you can’t make a double move up or down a wall).
If you do not reach the top of the vertical surface or find a suitable hand- or foothold, you must make a Climb check appropriate to the surface. If you succeed on the check, you can use this ability again in the next round. Otherwise, you fall or make no progress, as determined by the check result.
You can’t use this ability to traverse a ceiling or overhang.
Your purpose in the dungeon is to fight and guard against evil. The typical dungeon is full of wicked creatures and magic. Your detect evil and smite evil abilities are more likely to come into play in a dungeon than elsewhere. Take advantage of detect evil whenever possible to prevent surprise and give the advantage to you instead of to your adversaries. Use your smite cautiously — don’t waste it on a weaker being if you suspect greater evil lies ahead.
Lay on hands provides all-important healing and can give the cleric a chance to use offensive or support spells. If you encounter undead that are particularly hard to hit, using lay on hands as a touch attack can more effectively damage them and conserve your party’s resources.
Divine health protects you from diseases that can debilitate a party. When facing creatures or environmental hazards that can cause disease, stay in front to protect your companions. Your ability to use remove disease at 6th level lets you do even more.
For your spell selection, gauge the party’s overall capability to deal with damage, disease, and other ill effects. If they can easily handle those problems, pick spells that grant combat bonuses, such as bless, bull’s strength, prayer and holy sword. If not, cure and restoration spells, delay poison, shield other, remove curse and neutralize poison might be better choices.
Don’t bring your mount into the dungeon. Few dungeons are constructed to allow a horse or other Large creature to pass, especially with the added height of a rider, so a mount is usually only a hindrance (and faces unnecessary danger).
Most paladins form a special relationship with a celestial mount that aids them in battle. You, however, spend most of your time fighting below the ground or in enclosed spaces, where a mount is of little use. Instead, you have forged a bond with celestial spirits whose aid you can call upon when needed.
Level: 5th.
Replaces: If you select this alternative class feature, you do not gain the special mount ability.
Benefit: Upon reaching 5th level, you can call upon your deity for aid in the form of a celestial spirit. Using this ability is a standard action that does not provoke attacks of opportunity. See below for detailed spirit descriptions and rules.
Your paladin level determines which kinds of celestial spirits answer your summons. You can summon the spirit available at your current level as well as any that became available at lower levels.
| Paladin Level | Spirit Summoned |
|---|---|
| 5th-10th | Spirit of Healing |
| 11th-15th | Spirit of Combat |
| 16th-19th | Spirit of Heroism |
| 20th+ | Spirit of the Fallen |
The following entries describe how each of the different spirits function. Unless otherwise specified, all spirits share some characteristics, as set out below.
Spirit of Healing: This spirit increases your ability to heal damage dealt to you or your allies. When summoned, it can heal an amount of damage equal to twice the amount you can heal using your lay on hands ability.
To use its healing ability, you or an ally must begin or end your turn in the same square as the spirit. That character can then use a standard action to transfer some or all of the hit points from the spirit to herself. Once the spirit has used all its healing ability, it dissipates.
Spirit of Combat: This spirit enhances combat ability. Whenever an ally (including yourself) is adjacent to the spirit of combat or occupying its space, that character gains holy fervour. Holy fervour grants a +1 sacred bonus on attacks and damage rolls for every four paladin levels you possess (up to a maximum of +5 at 20th level). In addition, affected characters’ weapons are treated as good-aligned for the purpose of overcoming damage reduction.
Spirit of Heroism: This spirit automatically occupies your space and does not leave until dismissed or dispelled, or the duration of the summoning ends. You gain DR 10/—. In addition, you gain the benefit of the Diehard feat (even if you do not meet the prerequisite) and can use your lay on hands ability as a free action once per round instead of as a standard action.
Spirit of the Fallen: While you or any of your allies are adjacent to this spirit, it grants fast healing 10 to those characters. If an affected character’s hit points drop to 0 or fewer while within 30 feet of this spirit, it revives that character at the start of his next turn, allowing him to take his action as normal. The character heals an amount of damage equal to twice your paladin level, though if his hit points are still at -10 or below, he still dies. The spirit can use its revive ability once per round.
A spirit of the fallen cannot revive creatures whose bodies have been destroyed (such as by a disintegrate spell), nor can it reverse the effects of bodily changes, such as from flesh to stone or baleful polymorph, or other effects that slay a character without dealing damage.
Even in the dungeon, you excel at scouting and also provide combat support. Your Track bonus feat lets you find enemies who don’t want to be found, so max out your Survival skill to help with the difficult task of tracking creatures over dungeons’ stone surfaces. Most of the essential dungeon skills are in your class skill list, so you can become an ideal dungeoneer. Hide and Move Silently provide much-needed stealth. If the party has no rogue, focus on skills that will let you fill a similar role, and consider the Nimble Fingers feat to compensate for not having Disable Device and Open Lock as class skills.
When selecting a favoured enemy, try to anticipate creature types that are more prevalent in dungeons, such as aberrations, monstrous humanoids, evil outsiders, undead or vermin.
Dungeoneering need not make archery a bad choice of combat style. Sometimes a situation will simply not leave enough room to move into melee, making archery a powerful alternative even in cramped quarters. Take Point-Blank Shot and Precise Shot to nullify the disadvantages posed by small rooms and narrow corridors.
As with the druid, if you have an animal companion, select a creature with a special mode of movement, such as a badger, eagle or owl.
For your spells, stick with choices that work in a dungeon. Detect snares and pits, jump, pass without trace, freedom of movement and commune with nature speed travel and facilitate stealth even if you’re not outdoors. Barkskin, bear’s endurance and other ability boosters support your party with combat advantages. Remove disease and freedom of movement can deal with setbacks. If your party is short on healing, make sure to prepare plenty of cure spells.
Many rangers journey across the wild lands of the surface, but you are trained to descend deep into the earth.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain the Track feat at 1st level or the swift tracker ability at 8th level.
Benefit: You gain the trapfinding ability of the rogue. In addition, you gain Disable Device as a class skill. You can use the Search skill to locate traps with a DC higher than 20, and you can use Disable Device to bypass a trap or disarm magic traps.
Your purpose in the dungeon is, frankly, to do everything. You are the skill expert, and the rest of your party relies on your expertise. Other characters probably do not have Disable Device, Knowledge (Dungeoneering) and Open Lock, so make sure you have plenty of ranks in those skills. Increase your stealth with Hide and Move Silently, both for setting up sneak attacks and because you’ll often be ahead of the party, looking for traps — max out your Search skill as well. Balance and Tumble help avoid the (literal) pitfalls of dungeon delving.
You are the best character to disarm traps. Your class skills and special abilities let you deal with most traps easily. Don’t forget to purchase a set of thieves’ tools (preferably masterwork) and a 10-foot pole or other reaching device to test traps from a distance.
In combat, sneak attacks are your specialty. With Tumble, you can move through a crowd of creatures to set up flanking opportunities. The Acrobatic Strike and Combat Acrobat feats provide attack bonuses and reduce movement penalties while you are tumbling. Combat Reflexes, Mobility and Spring Attack all increase your combat options.
Sometimes only a few seconds make the difference between stopping the descent of a spiked ceiling and coming to a messy end. Through countless hours of practice, you have learned to make quick work of traps. But this speed comes at a price. Because you focus on disarming traps, you react more slowly when a trap activates.
Level: 3rd.
Replaces: If you select this alternative class feature, you do not gain trap sense +1 at 3rd level. Instead, you gain trap sense +1 at 6th level, with an additional increase of +1 every four levels thereafter (to a maximum of +4 at 18th level).
Benefit: When you use Disable Device to disarm a trap, the time required to perform the check is reduced. Use the following table:
| Device | Time | Disable Device DC |
|---|---|---|
| Simple | 1 move action | 10 |
| Tricky | 1 standard action | 15 |
| Difficult | 1 full-round action | 20 |
| Wicked | 1d4 rounds | 25+ |
Creatures that have immunity to extra damage from sneak attacks are a bane to rogues everywhere. Particularly in ancient tombs where undead are common, rogues must rely on their wits to survive. You have spent a significant amount of time studying this problem and have learned ways to harm even such resilient opponents.
Level: 3rd.
Replaces: If you select this alternative class feature, you do not gain trap sense.
Benefit: Whenever you flank a creature that is immune to extra damage from sneak attacks, you still deal extra damage equal to half your normal sneak attack dice. This benefit does not apply against creatures that cannot be flanked, nor against foes that are otherwise denied their Dexterity bonus to AC or flat-footed but not flanked.
Note: This class feature is the same as Expedition to Castle Ravenloft (Page 2085)
In the dungeon, as elsewhere, you are the blaster. With a limited spell selection, you’re better off focusing on damage-dealing spells — especially those that take advantage of confined space — than trying to plan for contingencies. Burning hands, flaming sphere, fireball, lightning bolt, cloudkill and chain lightning work best when enemies are close together (and prove the point that your party members shouldn’t travel in a tight pack). Also consider force and sonic spells, and those that ignore spell resistance (as many conjuration spells do), so you have the best chance of dealing maximum damage to any sort of enemy.
A few movement-enhancing spells, such as fly and dimension door, are certainly worth learning. For 0-level spells, light is always good, mage hand and open/close can test for traps, ghost sound can trick sentries, and arcane mark helps you find your way in mazes.
Concentration, Knowledge (Arcana) and Spellcraft are your most useful class skills. If you have some points left to spend, consider cross-class skills that are useful in the dungeon, especially Spot. When it comes to feats, Combat Casting will keep you from losing spells in a sticky situation, and Spell Focus (evocation) improves your offensive capability. Be careful about area spells that can harm your own party members; consider Sculpt Spell to leave safe spaces when you don’t have the opportunity to target your effects perfectly.
As a powerful spellcaster, you’re likely to attract the attention of powerful opponents, and your teammates can’t always protect you. Spell shield lets you use your spells’ energy to offset damage that might otherwise kill you.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain a familiar.
Benefit: By achieving oneness with the magical energy from which you draw your power, you make it part of your life force. As an immediate action when you take damage from any source, you can attempt to sacrifice spell energy instead of losing hit points. Expend a spell slot as if you had cast a spell of that level. Then, make a Concentration check with a DC equal to 15 + the level of the sacrificed spell. If you succeed, you ignore an amount of damage equal to five times the level of the spell slot you gave up. If you fail, you still lose the spell, but the magical energy fails to negate any of the damage.
For example, Hennet finds himself in the way of a black dragon’s breath. Although he succeeded on his saving throw, he is still going to take 22 points of acid damage. As a 7th-level sorcerer, Hennet can sacrifice a spell of up to 3rd level. He chooses a 3rd-level spell, so the DC of his Concentration check is 18. Hennet gets a result of 22 and magically negates 15 points of the acid damage, taking only 7 points.
Special: You can attempt to deflect damage as often as you wish, but you can make only one attempt per round.
Special: If an attack’s damage has multiple sources (such as that of a flaming sword, which deals both weapon damage and fire damage), you must choose which source to negate.
Special: If an attack must deal damage to have a secondary effect (such as poison from a snake’s bite), negating all the damage also prevents the secondary effect.
Your role in the dungeon is to understand and overcome. Decipher Script, Knowledge (Arcana), Knowledge (Dungeoneering), Knowledge (History) and Spellcraft all give you access to lore others might not have. It’s a good idea to coordinate with other arcane casters and Knowledge specialists (especially bards) to avoid needless duplication of expertise. For feats, Combat Casting is always a good choice, and your high number of bonus feats lets you focus on useful metamagic or item creation.
Your choice of spells depends largely on what type of dungeon you enter. You should always have some basic combat spells available, such as mage armour, magic missile and fireball. For the rest, pick utility spells, including illusions to trick guards, ways to escape dangerous conditions (such as feather fall), movement enhancers (fly, dimension door) and finders of hidden hazards and benefits (detect secret doors, arcane eye). Dispel magic negates many sorts of hazards. As you proceed through a dungeon, you can adapt your spell selections accordingly. It can be worthwhile to leave a spell slot or two open to allow emergency preparation for a specific situation, and the Alacritous Cogitation feat lets you do it on the fly.
You can use Scribe Scroll to prepare utility spells such as knock, detect secret doors, rope trick and gaseous form ahead of time, leaving space for more offensive power. The XP cost for scribing low-level spells is minimal, and the flexibility it allows is well worth the price. Wands of useful low-level spells, such as detect magic, feather fall and mage armour, are also handy.
You have attuned yourself to the motions of the cosmos. The sun does more than mark off the day as it travels across the sky. It alters the magic you command and the spells available to you. When in the sun’s warm embrace, you can cast one set of spells. When you journey into the dark, or when the moon hangs in the sky, you gain access to a second set of spells. This alternative class feature does not give you more spells to cast; it gives you more to prepare and choose from.
Level: 1st.
Replaces: If you select this alternative class feature, you do not gain a familiar.
Benefit: You can designate one slot per spell level above 0 as the union of sun and moon. When you prepare your spells, you can prepare two spells for one or more of these slots. Designate one of the two as a spell of the moon and the other as a spell of the sun. You can cast the moon spell only if you are underground or above-ground during the night, and you can cast the sun spell only when you are above-ground during daylight hours. If you cast one of these paired spells, it takes effect normally, but you no longer can use that spell slot to cast the spell from the opposite environment.
For example, Mialee is a 5th-level wizard with Intelligence 16. She selects this class option and prepares her spells for the day as follows. In the list, a superscript M denotes a spell of the moon, which can be cast only underground, or at night aboveground, and a superscript S denotes a spell of the sun, which can be cast only aboveg-round in daylight.
If Mialee casts daylight whilst underground, she marks that spell plus its environmentally opposite spell of the same level (in this case, displacement) off her list of prepared spells.
Source: Dungeonscape (Page 8)