The Fen Fiend possesses a mutable form of peat, mud, and stagnant water, allowing it to seep through wetland terrain undetected. It emits a chilling aura that lowers temperatures and thickens fog, disorienting prey, and its semi-corporeal nature enables regeneration from dispersal. Subsonic vibrations communicate its presence, unsettling both creatures and humans.

Serves as an environmental manipulator, intensifying fog density and triggering creature aggression near fen areas to test players' resilience and escalate horror through unpredictable hazards.