An Unknown in Act 3-7.
Unknowns are bosses that are made out of various machine parts and powered by a central red core. Essentially walking scrapheaps, they can shapeshift and crawl up walls and along ceilings. They appear in the game three times, with the first two inside the Kreon in Act 3-6 and Act 3-7, respectively. The third one appears in Act 4-5.
Abilities[]
Because some of the Unknown's parts are actually guns, it can use them to great effect. Shifting into a pose resembling either a snake or a tree, it will unleash all of its guns simultaneously, which usually ends up knocking Sam back (or forcing him into damage-triggered AR mode on higher difficulty levels).
Sometimes, the Unknown will assume the shape of a large claw and glow bright red, at which point it is highly recommended that the player boosts away from it. This is because it will lunge at Sam once or twice and if it catches him, it will perform a unique finisher in which Sam is grabbed and swiftly decapitated.
Tactics[]
Occasionally, an Unknown will extend upwards in a cone-like shape with its core at the very top. This provides a great opportunity for the player to attack, but beware the lasers that spread in random directions from the core; depending on the difficulty level, they either send Sam into AR mode or kill him outright.
If enough damage is dealt to the Unknown at once, it will fall apart, leaving its core exposed. The core will then start to run away on two legs while it slowly gathers its parts back together, leaving a decent window for Sam to perform a melee attack or simply blast it with a shotgun.
Unknowns are also vulnerable to the LFE Gun, with shots from the weapon dealing damage to the core even when it is protected.
Gameplay notes (from the description of this video):
"One of my favourite enemies of the game, it has that 'cute, yet deadly' vibe that I like on dangerous enemies. It's weak point is its core, which is not always exposed, but sometimes he does the 'Christmas tree' stance, giving you a good chance to shoot the hell out of it with the HMG. Of course you can weaken it, by blasting a few Shotgun shot on it. Soon the surrounding scrap will fall down, giving you another chance. But careful, if it 'blooms', and the core is flashing for a second, it means it's about to perform it's 'fatality' move, which is quite... painful, even to watch." —Vizi István