Guess the entity!

Rules: No april fool entities, no variations of the same entity. Removed entities are fair game but theories are not

1- This entity shares a trait with rush and ambush

2- This entity does not have any spawn requirements (this entity does not spawn at specific doors, does not spawn if an event occurs (like void when you're too far back or glitch when generation fails), etc...)

3- The entity is not insta-kill but it does deal damage (100 damage and above count as instakill)