[Coldsaturn]

If you use your resources to build Abysswalker a bit he might just drag you by force through all the battles and a few tens of orbit stages. There's a little gimmick you need to use with him where he spawns purple gems on the battle field and if you get them his charging bar goes up faster for his ult attacks. Also if you have more than one enemy (he has crowd control on top of everything else) he might put a purple gem on one and if you attack that target you also give him a solid boost.

I've also found this visual guide on which protocores are more useful for the myth companions