Brute

This huge block is the easiest enemy in the game. The only danger about him is his speed and strength (no locked doors can stop him). In all other cases he's very weak: ultimately dumb (any noise can distract his attention from the players), can't set traps at all, very loud steps and bright light out of his face (you'll be aware about his presence in advance). If you hide in room, Brute will check only one place in search of you.

Hunter

Tends to be the most formidable foe and the worst variant during the speedruns. Unlike other monsters, Hunter can travel through the ship via vents and appear instantly in case he leave green eggs. Hunter has an ability appear instantly even at the very beginning of the game. His steps are less louder and he is half-transparent, what can be a menace in dark rooms. Also, unlike other monsters, Hunter disappears in the nearest vent or even the side of the ship once the player run away. When you hide in room, Hunter can check up to two locations.

Fiend

Intelligent monster with purple aura around him. The most notorious danger about him is his smart behaviour: Fiend can set traps and catch inattentive players behind the nearest corner. Even if Fiend is very slow, his magic abilities give him an advantage in long corridors - he can block doors and freeze player on the plain view. The main weakness of Fiend is his aura - it causes all lights to blink once he appear near of it.

Hacks (the list will be updated once I get something new to share):

• If you let the Egg Timer ring properly three times, the next start of it cause instant ringing without a need to wait for 30 seconds
• The noise of working crane for Hunter seems to be more interesting than a working radio - Hunter even ignores the latter totally