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). 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.
If enough damage is dealt to the Unknown at once, it will fall apart and its red core will be left exposed and start to run away on two legs while it slowly gathers its parts back together. This leaves a decent window for Sam to perform a melee attack.
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.
Gameplay notes (quoted 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." -vizi02