Star Wars Episode XVI - Paths of Chaos
Rancor is the only self-aware, sentient, and force using kind of his species. A long time ago he was given powers by the Ancients in order to guard time and the general flow of the universe.
The Jedi and Sith both sought out Rancor during the war, but he refused to aide either side, eventually killing those that came to ask him for help in the war. He now resides in isolation on Dagobah and only the foolhardy who desire ancient wisdom and Force techniques dare to seek him out.
Seeing an end to all things by the Fulminar menace and aided by Qui-Gonn’Jinn and Daskar’Jinn, he broke free of his confines and aided in the final battle on Ithor. He has appeared as a force spirit even while being alive, and seems to have control over powers that none can quite grasp.
At the end of the war, as a gesture of friendship, he hosted a timewide tournament, allowing participants from all of time to come and fight against each other.
He helped to repair time after Hope destroyed it while trying to bring her daughters back from the dead, and aided the Heroes of Ithor (and others) to become ancients of the force in order to finally exterminate the evil ancient Mavick.
During the War of the Ancients, Rancor refused to take part, informing his comrades who were on both sides of the war that his job was to guard time and the general flow of the universe, and since they were the Force, whatever they did was what the Force wanted. It was obvious he was disappointed in all of their actions however, except perhaps Trinity who refused to fight.
It’s rumored he spoke with Croagnifit after Dia Ven was purged from the ancients body, but no one knows what the talk was about or what either of them did.