Environment any
Organization solitary
Treasure double standard

The phasm is a bizarre aberration. Its normal form is an ovoid blob of protoplasmic material, but it spends most of its life imitating humanoids. In this form, a phasm acts on its whims, exploring, adventuring, stealing, living an existence of aesthetic deprivation or hedonistic indulgence. Each phasm is different, and may change personalities within a single lifetime. A phasm may attempt to take over a kingdom simply for the thrill of the experience, while another might found a religion based on service and generosity. However, all phasms derive the greatest pleasure from fooling other creatures about their true nature.

If discovered, a phasm first attempts to slay those who realize it is not what it appears to be, though it might also negotiate if it believes there is greater benefit to doing so. In combat, a phasm employs whatever weapons and items it has at hand. It only uses its slam attack if unarmed. If it can’t defeat opponents in open combat, a phasm resorts to subtler means, such as poison, curses or assassination.

A phasm also uses its ability to change shape to aid itself in combat. Against creatures it intends to slay, a phasm assumes the form of a dragon or other dangerous beast. If it needs to flee it changes shape into a swift animal.

While impersonating a humanoid, a phasm often accrues class levels in fighter, rogue or wizard. Due to its whimsical and mutable nature, a phasm loses these class levels after a few years, especially if it takes up the role of a different individual. The average age of a phasm is 2d4+3 (x100) years, and there is no known limit to how old a phasm can grow. Families of adventurers report engaging in generations-long battles with individual phasms, the creature plaguing grandfathers, fathers and sons.

A phasm weighs about 400 pounds, and appears as an ooze in its natural form. Dark spots on its body indicate the presence of sensory organs.