That great being was...
The Dweller in Flame; the Burning One; the Living Flame!
Cthugha!
A Great Old One shaped like a moving stellar sun!
As for Hastur, whom Yog-Sothoth had commanded, he was a mid-ranking Great Old One himself.
Watching the battle from afar, he would not actually be affected much.
Indeed, so long as he did not get involved, suffer a sudden lapse of sanity, and charge into a head-on fight with the Grand Supreme Heavenly Demon!
Then there was a ninety-eight percent chance that he would be fine.
So would he willingly travel past dozens of small thousand worlds and several middle thousand worlds, across a distance spanning a great thousand world?
And go watch in the very middle thousand world where his loathsome cousin lived?
"Impossible!"
Hastur roared in the language of souls, his tattered yellow cloak stirring up a surge of cosmic rays.
Frenzied orange-yellow rays furiously struck a field of cosmic meteorites nearby.
Instantly, those meteorites, fragments of some unknown planet, suffered utter annihilation.
They were reduced straight to even finer cosmic dust.
But as a mid-ranking Great Old One, Hastur was not his cousin. Vast disparities existed within the hierarchy of rulers in the Cthulhu mythos.
Unless they were among those particular few with the combat strength of a Middle Great Old One.
Otherwise, they could not possibly fight the mere three Upper Great Old Ones in existence.
And Hastur clearly was not one of them.
As for that exceptional Middle Great Old One who had close dealings with him and could challenge Upper Great Old Ones across the gap in rank.
That being was also on particularly bad terms with him.
Namely, Cthulhu.
A creator, a terrifying fellow who was the first-person incarnation of the great Azathoth within his dream!