I have found the over powered strategy!
Summons are honestly super op, esp with 5 mana cost cementary that you can loot from lich. Skeletons are also super great.
How the strat works:
Pick creed of impulse, you will need the mana regen and won't be aiming at the end. Any boss that spawns extra enemies you take a card, otherwise take an artifact. Take mana artifacts (most summons cost 3+), and mostly filler is fine.
If you see gravekeeper don't loot a card, loot for artifact. He has a reasonable drop chance for a spade (it might even be guaranteed if you don't have it), and space gives u +3 dmg with little boss empowering.
Good bosses to loot:
Keeper of Cantharus: He has a laser summon! free dmg
Mucelian Patriach: Has a blight spawn that is good for tanking
Ash dude (forgor his name): He has a wizard summon who shoots fireballs.
Melee Bosses really like going after your summons, which means they stop being so much of a problem! You can kinda just sit back and just dodge the aoe weaponry after you start spawning in your army.
Ranged bosses just get overwhelmed and brutally slaughtered.
Basically built my own raid force by taking only summons.
I would've gone further if I had more time (died intentionally just to get to the end screen). Will send an update of how far I can get.