I wonder if there is a way to have a creature die if you take its picture?
a few more suggestions:
*A creature that mimics the player movement pattern but inversely, leading to perfectly symmetrical violence if one doesn’t catch on to what’s happening
*A non-hostile creature that seems chiefly concerned with destroying buildings
*A creature that poses as an NPC eager to join you and behaves as exactly that. Over time it gradually learns your skills growing more formidable and treacherous. Maybe as it attains certain power thresholds sneaky spelling errors in its dialog start to give it away?
*A creature that SPECIFICALLY targets the arms and legs and will NEVER do damage to the head or torso. Optionally, once a broken limb lies vulnerable the creature attempts to replace it like a living prosthesis–requiring painful self-surgery to remove if one isn’t willing to play host.
*A ranged attacker that hops around at random. Being struck with its attacks causes the player to hallucinate multiple manifestations of this menace–making it difficult to ferret out the location of their actual attacker
*Sponge like, immobile creature that quickly duplicates in favorable conditions: i.e. rain. God forbid it reaches a riverbed.
*Creature that converts structures to meat much like the paper wasp does.