how to write a metaphysical fight scene

so i have this book i'm writing, in witch the final battle is basically reality itself fighting an eldritch god. i'm having trouble describing such an event, as most of the events are rather abstract, and could use a little help.

Tricky... I say take the cosmic horror approach and avoid describing as much as possible. Have what little you do say be short and somewhat nonsensical like you're using a metaphor for something that can't be described. " Reality screamed..." "The Thing turned in on itself..." "Like the laws of physics realized such a thing couldn't exist." That sort of thing.

Perhaps try a bit of generalizing/metaphors, something like "The Thing struck straight for the heart of the universe" and "reality resisted, pushing the assailant back whence it came". Basically, try describing a fight between two human characters in as general terms as possible, so that the reader would have to imagine all the moves: - the enemy launched an attack - the hero stopped it with effort - the enemy pushed on - the hero managed to turn tables on the enemy - the hero drove the enemy back - the enemy was pushed into defence - the hero slowly overpowered the enemy ...and never specify much beyond this. Don't describe what exactly is hapenning, but what it means for the fight.

Describe the observable effects the battle has on reality, and its closest equivalent on the entity.

What this guy says is probably good advice; have it described as the characters can perceive it. If they can't, milk it for suspense.