Spirit troll

A spirit troll was a very intelligent and rare creature brought about by the magical interbreeding of trolls and invisible stalkers.

They were also spawned when a troll regenerated from being blasted with psychic energy, causing them to take a nonphysical form. Spirit trolls were sometimes unaware of this transition as they were still able to employ their teeth and claws, instead attacking their victim's mind.

Description
These invisible half-breeds looked similar to trolls, but had diffused features. They had an acute sense of smell and superior infravision.

Spirit trolls were said to be odious mutations of spectral trolls. These creatures were very dexterous and were immune to becoming exhausted, grappled, paralyzed, petrified, and falling prone and unconscious. They could move through other objects and even creatures.

Combat
Spirit trolls could only be damaged by magical weapons or fire. They regenerated and attacked with their sharp claws, as did other trolls. They also attacked with vicious bites with their fangs, and could even stun foes. They were resistant to acid, cold, fire, lightning, and thunder.

History
The secret of their creation was believed to have been lost, and only thirty or so were known to exist.

Appearances

 * Video games
 * Baldur's Gate II: Shadows of Amn