The Bestiary Malitiae: Mimics
I've had this creature stuck in my head for the last week and needed to make it real, so here it is, made for mork-borg, but you could run it in any game with some adjustment.
Wander deep enough into the forest that the songs of the rustling trees become all you can hear and you might find them singing a very different song. The wispered suffering of your loved ones — uncannily real — begging you for help. The mimic is a parasitic network of fungus, trees and razorvines that pull and stretch their victims vocal chords to lure in new prey.
HP 60 Morale - Thickened Bark -d4 Grasping Razorvines D8 or Special
Special: After killing its prey, it begins to puppet the corpse, all players do a dr 14 presence test. On failure, they panic and their attacks target a random combatant.