He is the pope guy who sells all sorts of good items for heretic souls, including the DD potion. Speaking of which, I should probably add contrite to his inventory too if that's your favourite. 😂 The normal potion vendor (Pseudo-Gerber) can sell dupes.
I do have a dev build up at https://games.sahaqiel.com/cc.html if you wanna play around and try to see how you've made it get stuck. Basically you can skip to the fourth boss level by hitting E (it also gives you a bunch of 4-way PB tiles). You can get free relics/cards by hitting P/C. It's random though so might need a bit of cycling around to find smite or what ever you want. Basically almost all keys do something. 😅 Umm what could be important... K kills random heretic and D redraws one tile from the deck.