Rushlight

When it can be seen at all, a rushlight is a flickering, nearly clear globe of fire holding the face and hands of a tormented spirit. It cannot speak but seems to understand the languages it knew in life.

Looking straight at a rushlight reveals nothing; it shows only at the edge of vision. A player who says the character is using peripheral vision can make it out, but attacks still suffer -2. Detect invisibility and similar magic reveal it fully.

Its flame gives off little light and no heat anyone can feel, yet it is deadly. A hit deals 3d4 damage, and each item the target carries must save vs. magical fire or be destroyed. The victim's flesh then smolders, taking 2d4 damage every turn afterward. Water, smothering with a cloak, and other mundane methods fail; only dispel magic or similar magic douses it.

Only magical weapons or creatures of 4+1 Hit Dice or more can strike it, and it ignores spells affecting body or mind as well as cold and fire spells. Though arguably undead, it cannot be turned, yet each flask of holy water that hits it deals 2d6.

A rushlight forms when an evil person is burned alive on a funeral pyre and its fleeing soul fuses with the flames before it can escape. By day it rests sunk in the earth where it was cremated, as it must. At night it wanders up to twenty miles from that spot hunting travelers, driven by a belief that killing will ease its own agony.

It never rests, and it seems to draw strength from the terror and pain it inflicts, growing livelier after its first few victims catch fire.