But if they force him to a situation where he cant attack or make a move hes lost. I know this is not chess but if oryx is forced to escape to the other dimension where he can not directly influence the battle he would lose all his forces and the world would be gradually flood-a-fied and once it has he would stand no chance. remember if the flood make a gravemind they will all share eachothers knowledge and they obtain the knowledge of any person a flood takes over. So if a flood took over steven hawking for example they would all possess the same knowledge he does. Obviously steven is not alive in either universe its just an example

If he starts that battle in his universe their is nothing anyone can do to kill him, reality warping battles are stalemates.

But why would anyone besides oryx be in his personal dimension and im not sure if it was stated that1 he is unkillable in his dimension 2 all powerful in his dimension 3 is the master and controller of that dimension rather than just an inhabitant of it 4 has a physical body while in it. I got the impression that at the end of the campaign he fled to his dimension because it was a safe location where he knew he could not be followed or that it was a john carter like scenario were he was projecting himself rather than physically in the earth dimension and he was retreats to prevent is projected self from being destroyed as he can be killed while in the earth world as seen during the raid. Which i assume would permanently kill him