Hunter Long Legs

Hunter Long Legs is a rare creature in the Downpour DLC, which spawns under specific requirements exclusively while playing as.

Appearance
Hunter Long Legs takes the appearance of a reanimated corpse overtaken by a mass of flesh-coloured tendrils, similar to the Rot(⋅⋅). Individual instances of HLL have varying appearances which depend on its internal variables. Due to this, the appearence of HLL varies from cycle to cycle. This can be assumed to be a feature of the Rot cysts on 's corpse swelling and then contracting or bursting as time passes, as the Hunter Long Legs is a unique creature, and should otherwise have a fixed appearance in a given playthrough.

Spawning
Hunter Long Legs spawns only when playing as, if the player has failed a run on the same save slot. It then spawns in the same room as that run ended.

Trivia
It can be assumed that this is what happened when hunters time "ran out" as stated by LttM