Phantoon

Phantoon is an alien ghost and a boss in both Super Metroid, and Metroid: Other M.

Appearance
Phantoon is an alien ghost. His entire body looks like a grey alien's head and has green skin. He also has tenticles for arms, and an eye surrounded by teeth that's his weak spot.

Super Metroid
Phantoon made his first appearance in Super Metroid. Samus fights him in a wrecked ship. Phantoon fights by teleporting at random areas and producing ghostly fire. Eventually, Phantoon's eye opens, giving Samus a chance to shoot at Phantoon. After Samus defeats Phantoon, Phantoon dissappears and the wrecked ship's power is restored.

Other M
Phantoon only appears in the post game version of Other M. He's out for revenge and has changed a lot. Phantoon is roughly twenty times bigger than before, and has a bigger arsenal to fight Samus with. Phantoon summons ghostly hands to attack Samus, creates giant pools of darkness around the area, and he shoots homing ghostly fireballs practically non-stop. Phantoon's main weakness is his eye, and after Samus defeats Phantoon, he drifts into space and explodes.