Xucubi

The Xucubi are an unseen and unmentioned enemy faction in the non-canonical Nazi Zombies storyline Apocalypse IV: Imminent Impact.

Origins
The Xucubi are said to be the true creators of the Universe and the Human race. When they first appeared and where is unknown. Their exsistence has only been confirmed by writing on the walls in the catacombs of the Moon describing their lifestyle, technology, and partial history of their exsistence. The writing describes that they were always around and are the superior being. It has also been said that they originated from the Fourth Dimension, also known as the Multiverse.

Technology
Their technology enables them to create entire galaxies within fractions of seconds, travel at the speed of light, time travel, redux, and safely travel through wormholes/blackholes.

Lifestyle
Their lifestyle is depicted as being similar to that of the Humans (which further supports the theory that they are the true creators of the Universe); government structure, military, and cities. Their diet is unknown, but according to the writings in the catacombs they were known to be cannible, often eating their dead comrades.

Extinction
Sometime around 100,000,000,000 B.C., the Xucubi went extinct. The cause of their extinction is unknown. It isn't even confirmed that they actually went extinct, with a possibility being that they left the Moon and went back to the Fourth Dimension.

Legacy
The Xucubi live on through Luna Zombies, a type of zombie that was created when Element 115 came into contact with Xucubi blood.

Trivia

 * Judging by the fact that Luna Zombies have four tentacles that protrude from their mouths, it is possible that Xucubi also have tentacles in/near their mouths.