Sakaar in the 40K Universe was more like the MCU version: a gladiatorial arena run by the Grandmaster. That nasty old bastard had no other hobbies; he just loved watching gladiator fights and gambling on them.
The so-called Elders Of The Universe were actually the first batch of highly intelligent Humanoid Races to emerge after the Big Bang. They were also one of the universe's oldest life forms, living in the first galaxy formed after the universe's birth.
But being born early did not make them invincible. These people tragically lived through the Creator War, the super war that erupted after the Solar System and Earth appeared, with Oshtur and Gaea fighting Chthon and Set.
Atum, the God Eater created by Gaea, relentlessly slaughtered Chthon and his followers. From Earth to the entire universe, battlefields were everywhere. Countless galaxies were shattered and destroyed by the aftershocks of their clashes, not to mention the ancient civilizations in the primordial galaxy.
The members of the Elders Of The Universe were all the last survivors of their respective races. Each possessed immortality and mastered incredibly advanced ancient technology, which gave them the ability to flee their homes at the time.
Yet as though arranged by some invisible will, only one person escaped from every primordial civilization.
Of course, some had no one escape at all. But if there was a survivor, the number was always one.
After these survivors discovered one another's existence, they began contacting each other and sticking together for warmth. Though they belonged to different races, their shared misery made them see each other as brothers and sisters. They fled together, studying how to survive amid a god war that could destroy heaven and earth.
The first god war ended with the White Magic side victorious. Oshtur left the Main