I had fun with poison self for shields, double shields, and flip status to opponent combo.
Real MVP was wave collapse healing. EDIT The dumb opponents card was even better.
I wish there was a way to pay to remove cards from deck or else something else to pay to upgrade came up. From the comments apparently there was a card for that, but I never encountered it, which suggests the frequency might be a bit low.
I ignored money gain, and did okay. Not losing any universes was more important, and I managed a perfect run until princess.
In the main game, there is a ‘secret’ boss fight, sort of.
I got whacked because I found it before I fought anyone else and had no items!
Edit: Beat the boss, but I didn’t fight the last mainline boss! It ended my run!
Edit I also feel like using eye-contact on Medusa ought to have a side effect, lol.