Nilgh'rishuggogg is an Outer Beast, similar to the Outer Gods in that it would roam the outer space, but vastly more powerful than all of them, even The Blind Idiot God himself. It is to them like a wild apex predator to humans.
During the war between the Elder Gods and the Outer Gods - Great Old Ones, the beast was created to turn the tide of the battle. Although, it still remains unknown to this day which side created the beast. Some argued that it was the Elder Gods' one heavy hit to crush their enemies all at once, while some others believed the Outer Gods and Great Old Ones made it to fight back their slavers.
However, one thing that was clear and in common, was that the monster was made to be a weapon of mass destruction in "living" form, but its true nature is that of a wild, savage, primal, untamed beast. Unleashed into the cosmos, it did not hesitate to prey upon the Gods of either sides, even devouring the remains of the dead ones to satiate its hunger for power. In so doing, it grew unimaginably and unspeakably powerful, as well as vast in its size, each of its tentacles so near-infinite that could contain galaxies within.
Like an insect, it quickly and rapidly gave birth to hordes of galaxy-sized monstrosities, dominating the entire cosmos with its overwhelming "colony" of "hatchlings". The Elder Gods and Great Old Ones had to join forces and banish it to the absolute far edge of the universe, where not a single spark of starlight was visible in sight, where not even a speck of light of a massive quasar could be seen. Some of its "hatchlings" survived the Gods' joined-force assault, but were captured or even devoured by them to prevent it from returning.
For billions of millenia to come, the cosmos was safe from the monstrosity, but it was simply because the monster was waiting for the right time to escape, and it had already got a "signal"...
Doom has come to our family.