What after 1000?

Hello guys,

how do you progress in the game after reaching 1000? I started over on hard difficulty but can't get past level 125. Unlocked the three rebirth features (double enemy combat speed, auto combat for the main and row enemy spawn) and all the mercs avalaible with rebirth stones. Actually playing snake main, but can't survive. I tried several team compositions but i'm lacking damage. Should i restart on normal? Can someone explain me how to progress further in the game? Sorry for my bad english and thanks for the answers!