The Moon Pool

I'm a big proponent of including locations of special interest in my dungeons. Generally, these are mysterious and/or beneficial places that hold something that brings the characters back to it again and again. An oft-mentioned example of this from the Dwimmermount campaign is "the Cleric Tree," a weird, azoth-warped subterranean growth that, if properly tended to, yields "fruits" that function as potions of healing. Early on in the history of the campaign, the party discovered this growth, unlocked its secrets, and regularly returned to it in order to take advantage of its boons. In practical terms, this meant that, even as the characters delve deeper into Dwimmermount, they still have reason to return to earlier levels, which in turn gives me the opportunity to present the place as a living environment rather than a static one that can be "cleared" with enough effort. To my mind, this presentation is one of the key differences between a "megadungeon" (or campaign dungeon) and a mere "dungeon" (or lair).

Another special interest location is the Moon Pool, a shallow pool in a series of caves inhabited by a tribe of mutant kobolds. The cave in which the Pool is located has a small opening in its roof through which moonlight can shine, reflecting in the Pool. The Pool itself holds what alchemists refer to as "true water," a primordial liquid untainted by physical contaminants and that cannot be destroyed or have its state altered. Thus, it does not evaporate and cannot be frozen with even the mightiest of spells. On the other hand, true water is a supernatural solvent (which is why alchemists prize it), dissolving magical energies within itself.

In the case of the Moon Pool, the magical energies it dissolves are moon rays, called "lunar emanations" by sages. These moon rays may then be imbibed by living beings who partake of the Pool's contents, boosting -- or diminishing -- their magical potency, in accordance with the phases of the moon, whose power over magic is well-known. Drinking from the Moon Pool has the following effects:

Random Roll (1D20)	Lunar Phase	Effect
1-3	New Moon	-1 caster level, -1 spell (lowest and highest levels)
4-5	Waxing Crescent	+1 caster level
6-8	First Quarter	+1 spell (lowest level)
9-10	Waxing Gibbous	+1 spell (highest level)
11-13	Full Moon	+1 caster level, +1 spell (lowest and highest levels)
14-15	Waning Gibbous	-1 caster level
16-18	Last Quarter	-1 spell (lowest level)
19-20	Waning Crescent	-1 spell (highest level)

"+1 caster level" means that, for spells that have variable effects based on level (e.g. fireball), the caster is treated as one level higher than he actually is. "+1 spell" means that the character gains an additional spell of the type indicated (lowest/highest level) for the duration the Moon Pool's infused water is in effect. Obviously, effects stated as a penalty (e.g. "-1 caster level") function in reverse.

A character who drinks from the Moon Pool must make a saving throw against Spells or Radiation. Success indicates that the effect listed above is operative, according to the current phase of the moon. The effect lasts for a number of days equal to 1 plus the difference between the saving throw number and the number rolled by the player for his character. For example, a 6th-level magic-user requires a 12 to save against Spells or Radiation. If his player rolls 14, the appropriate effect lasts for 3 days. Failure means that the appropriate effect is not operative and no subsequent drinks from the Moon Pool will have any effect whatsoever for a number of days equal to the amount by which the character failed his saving throw. For that matter, while one effect is operative, subsequent drinks provide no additional effect, good or bad. Finally, Moon Pool effects cannot be dispelled by any known means; a character who has drunk from its waters must wait until the appropriate number of days has passed before its effects will fade.

I keep pretty good track of time in my campaign, using the guidelines given in Volume 3 of the LBBs. Consequently, I know roughly what phase the moon is in if it ever becomes pertinent to play. However, not all referees are as fastidious about timekeeping and so the table above can also be used to randomly determine the current phase.