Will O'Wisp

Will o'wisps are spiteful beings of the swamps, bogs and moors. Out in the wild they usually look like softly glowing balls of light, and because they can adjust their size, shape and color somewhat, they are easily mistaken for a lantern, a light spell or another man-made glow. When not attacking, a wisp can snuff out its light completely for 2-8 rounds, becoming invisible to anyone who cannot detect invisible things.

Their language is entirely visual, a code of color and brightness shifts, many too faint for an ordinary observer to catch. Since this is nearly impossible to imitate, talking with them is very hard. A few exceptional wisps have learned a simple spoken language, producing sound by vibrating at high speed, which gives them a thin, ghostly voice.

Wisps would rather guide prey into the fatal mire around them than trade blows, but when cornered they are dangerous and must be handled with care. A fighting wisp shifts its glow to pale green, violet or blue. They are nimble fliers that can hang still in the air, often posing as a beckoning lamp, then move in quick dashes or slow, lazy drifts.

Its real weapon is stored electricity. Diving in to graze a foe, it releases the charge, and a hit costs the target 2-16 hit points.

Physical weapons damage it normally, but spellcasters find their magic almost useless. Maze, magic missile and protection from evil are the lone spells that touch it. At 5 hit points or below it tries to escape; if it cannot, it surrenders and offers whatever treasure it has to buy its life. Given its chaotic nature, any deal struck with it is unreliable.

Most wisps are met alone, but 10% of the time up to three gather near an especially good hunting ground and cooperate to drive victims into the traps they have prepared.

Though hard to prove, the evidence suggests its food is the surge of electrical activity in the brain of someone who realizes, in terror, that death cannot be avoided. To stretch out that suffering and the meal it provides, wisps favor luring prey into quicksand and similar places that promise a slow, horrifying end.

The bog and swamp environment clearly matters to the creature somehow, though exactly how is unclear. Most likely the eerie, brooding atmosphere of such places deepens the dread of its victims and so increases the energy they release before dying.