the name of said game(if you hadn't noticed) is Nightmare Tag. in summary, Nightmare Tag is a VR PVP horror ASYM game where you can either: become the human and survive the "shared dream" while completing the objectives, working together with your teammates, venture through liminal spaces, and run from monster, or you can fight back. or you can become the nightmare and kill all the humans to win.
and this player monster is known as the "Mimic" (for obvious reasons.) also i recommend to play it if you have a VR.