Inspired by @connman116 and @mfcjpg (and thanks to @FleshHuman (A.K.A. D99) for unlocking Nightmare) - finally figured out how to get nightmare victories in current build. I can retire now :D.
Goal was "buy as few cards as possible, only buy the smallest number of cards you need to win the final level" -- which was 2 x axes + 2 x wrenches + any of the 0-cost-pickup-1 cards I was offered (only one in the end). Everything else was because I was waiting for wrenches.
I got the yellow cube at about 16 strength, and just kept upgrading using the freebie.
I got the 0-cost 17-scorium by tumblering a basic scorium to get rid of it.
