Hunter

This malevolent creature is humanoid in form and attacks by slashing you with its arms. It also phases between normal humanoid form to a particle like form, making it almost invisible from afar. It is an extremely aggressive creature, and it flanks you continuously by teleporting behind you. The Hunter has a HP of 2000 and Shield of 1500 at normal difficulty.

Repetitive attacks can cause it to be stunned temporally stopping it from teleportation

Also this creature spawns throughout the game and a staker-ish like theme noise can be heard when it has spawned in your area but hasn't detected you. (Hint. Remember locations where you spotted the Hunter, as it spawn location never changes!)