Or alternatively, he wants to combine the cosmic forces against Reality, since that is the outside force from his perspective. He fears that the disparate cosmic forces will be too busy infighting to be able to stop us when we eventually unleash our true potential or whatever.
Would make for an interesting "twist" if the one thing he feared the most was always us and our murderhobo ways. I think that would put a nice spin on the whole First Ones debate if the big mystery is why they created six flawed cosmic forces and seemingly deliberately let a seventh one grow organically without much input.
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It's almost definitely reality, the world that isnt a part of the six cosmic forces. It's described as "opposite" the six cosmic forces, both combining them and being in opposition, which is almost exactly what we see with our player characters.