Octabrain

Octabrains (often mistakenly called "Octobrains") are floating triclopses covered with beige skin. They are allied with several other extraterrestrial species in a menacing conglomerate that have invaded Earth, only to be defeated by Duke Nukem. They apparently prefer dark, dank places, and are almost always found within mutated areas.

Physiology
While they do possess six squid-like tentacles that hang below their massive heads, these seem to have atrophied from lack of use, and may or may not be vestigial. Instead, they have become extremely potent in the abilities of psychokinesis, likely brought about by the massive brain size they have acquired. The orbs travel somewhat slowly, however, and so Octabrains will often gang up on a victim to ensure at least one of their projections hit their mark. This ability allows them to project a powerful mental energy orb that can easily bring down a foe. This is only done at a distance, however; when at a point-blank range, they will instead deliver a strong bite with their large mouth and vicious fangs, although whether they're trying to eat their opponent (potentially to supply sustenance for their huge brain) or just kill them is not readily known. Unfortunately for the Octabrain, charging their psychokinetic power needs a moment to charge, and is obvious to an educated opponent as their brain and eyes will both glow bright red.

Two ridges of spikes run along the middle of the top of their head and body, and two equally-spiked mandibles flank a large mouth full of a full complement of dagger-like teeth. Most of the head-body is taken up by its massive brain, and is the most obviously important feature of the creature. The size of the brain may indicate that they are the most intelligent member of the conglomerate that they are aligned with. Their skin may be susceptible to injury, and they can noticeably flinch after being attacked.

They are amphibious creatures, and are equally at home in and out of the water. What with their psychokinetic abilities, it is possible that they can create an orb of influence that may cover their body skin-tight and allow them to continue breathing wherever they may wind up.

Link Between Octabrains & Protozoid Slimers
Octabrains follow a peculiar agenda not seen in any other species amongst their conglomerate: they can often be found guarding nests of Protozoid Slimer eggs. This leads mankind to speculate upon their relation. While they might just be specialized for guarding these eggs and perhaps use their mental powers to train and condition the Slimers to become killers while still incubating, there is also rumors in circulation explaining a completely different and more complex reason behind this.

This second theory states that Octabrains and Protozoid Slimers are in fact genetically related, possibly even being the same species. Like Octabrains, the Slimers have the presence of a brain inside of their semi-gelatinous body. However, these theories cannot be confirmed or denied with mankind's current knowledge of these mysterious organisms.