Enderman

Endermen are frightening monsters; while not from another planet they are from the End, another dimension adjacent to our own. Though not directly hostile, they are apparently extremely territorial and will attack anything that looks them in the face or that attacks them first.

Out of Universe information
Many sketches on YouTube have shown them as having purple blood but this may not be true [because they are just from a game]. Similar to their blood they have purple eyes. Though from the End they can spawn in the overworld and in the underworld with a spawn egg or commands or spawner. They have the ability to teleport and have glow effects like a nether portal, they are allergic to water and can be damaged by simply stepping into it. They fight skeletons if they are shot and are attacked by iron and snow golems. In a video on YouTube by the yogscast they referenced Endermen being the aliens in the other planet they were on in a custom map [really the End]. Endermen were commanded by the boss, Enderdragon also from the End. Upon death Endermen will drop ender pearls that can be used to find the End portal or to teleport. Endermen do not attack in creative mode and do not spawn in peaceful. There is a mod [modification] for the game that adds Enderfarmers, and a mod that adds Enderladies, some 3D and look like women and others normal Endermen but with a female animation viewed upon right clicking. There can be a Mutant Enderman.

Trivia

 * The Endermen were based on the cryptid monster, Slenderman, which is best known for appearing in a series of popular memes and as the antagonist of the PC game Slender.
 * The End world could just be a destroyed planet that could used to be colonized by Players, but then the Endermen could destroyed it with the Ender Dragon.

Appearances

 * Minecraft