Brain Flayers

Brain Flayers (開明脳者ブレインフレーヤー) were a species of very powerful interdimensional beings that could travel or transport other characters through other dimensions or timelines. They were formed from the energies of the Forbidden Gods and Final Gods that corrupted and merged with the Mana, the source of magic in the Mahou Kaiju Series universe. One first appeared in Kaiju World War: Part 1 where he was responsible for stranding the Sakura Igawa from Another Universe in the Main Mahou Kaiju Series Earth. They played a far more prominent role in All-Star Taimanin and Kaiju World War: Part 2, where more of them would come from a doomed future a thousand years from the present.

Multiversal Collapse
Even before the creation of the universe, a great war waged between the Ancient Gods, Worldeities and the forces of the multiverse, against the Final Gods and their endless armies of Forbidden Gods, Brain Flayers, Zeniths and Unknowns, which are rapidly consuming all of reality. After the invading Final Gods were repelled, in desperation, the Ancient Gods sacrificed all their power to gather several remaining universes in a pocket dimension and merge them to form a new and stronger one to grow for billion of years, so that they could have time to recover their powers and finish the war against the Final Gods anew.

However, the new universe was somewhat already unstable due to being a fusion of several universes, many of which were incompatible with each other. As such, the chaotic malice of the Final Gods and Forbidden Gods were able to seep into the small cracks in the universe and enter reality. These energies of evil would infuse with Mana, the omnipresent source of magical power in the universe, and create countless Brain Flayers in the span of billions of years. One of the very first Brain Flayers would be Shangri-La, who would also become the first Zenith, since it was formed also as a manifestation of the conflicting thoughts of the Ancient Gods who were able to come into existence in the cosmos' early eons. From Shangri-La, more Zeniths would be created.

Appearance
Each Brain Flayer has a different form but a majority of them have an octopus-like head, long hands, and/or tendrils coming from their bodies. There are also very unique-looking Brain Flayers, such as Antoma Tan Gendo, which was orb-shaped.

Abilities
Brain Flayers are beings that are formed from the corruption of Mana, the source of all magic that flows across the cosmos, by the void energies of the Final and Forbidden Gods seeping into the universe, and that mass of corrupted Mana would morph into physical entities, with powers that surpass the bounds of time and space.

They have the ability to conjure portals and cross from one dimension to a different one, or from a period in time to another, without problem.

They can create Unknowns, beings that, like their creators, have no consciousness nor emotions and only act upon the will of their masters.

Behavior
They view lower races in the universes, such as demons, humans and almost all alien civilizations, as pets or vessels to become Unnoises at best, and since they exist outside the boundaries of time and space, they have no capacity to display any emotion. Most of them are single-minded to achieve only one goal, to enslave, subjugate or annihilate entire worlds, acting no other impulses other than to dominate and destroy. However, just like Zeniths, exceptions can exist and they can gain emotions, such as Marjaana, a Brain Flayer Queen, who has rejected their violent ways and gone to live in peace in the Underworld. Most speak in their own language and can not be understood normally. Under them multiple species serve, such as the Brain Seeker or Brain Dogs but also cyborgs and magical Golems.

Differences with the Forbidden Gods
Brain Flayers and Forbidden Gods share several similarities. For example, both groups are interdimensional aggressors with the desire to invade or destroy dimensions with their immense power, and are viewed as existences beyond the comprehension of mortal beings. While a Brain Flayer or a Forbidden God can have multiple iterations, they don't have counterparts on other universes.

However, while the two species are extra-dimensional in nature, Brain Flayers are not transcendental like the Zeniths or Forbidden Gods. The Forbidden Gods were formed from the transformation of celestial or spatial bodies such as planets, galaxies or entire universes into evil entities through the malice of the Final Gods, representing the "corruption of worlds" and the "insignificance of life before greater unknown forces", while Brain Flayers are created from the materialization of Mana into new beings from the energies of Forbidden and Final Gods, representing the "corruption of power" and the "downfall of civilizations". In fact, there are several instances where Forbidden Gods created Brain Flayers specifically to obey their wishes, which was simply to conquer everything they see and slaughter all that would defy them.

Trivia

 * They are based on the Illithids from the Dungeons & Dragons series, who were also called "Mind Flayers", and are beings who see themselves as the dominant entities of the multiverse, desire to invade, can feast on the brains of weaker beings and use powerful psionic abilities.