Room Identification[]
Regulus' room is rather maze-like with dog-legged walls at the center corners.
Because of this shape, it's rather easy to get yourself backed into these corners and get mauled by the minions.
Strategy[]
Because of his bombardment attack that hits very often, it is not advised to face Regulus head-on. Instead, keep running (with Shift) in circles around the room and creating a safe distance, then shoot him from afar. Run away again as he closes in on you. Just be careful not to get stuck on map props as you strafe backwards.