I'm just gonna try to shove "Slay the Spire" and "Munchkin" into one game while pushing extra focus on cards relevant to our Monster Compendium theme. Not putting too much focus on trying to balance the game right now, gonna figure it out live during playtests.
Prototype Research: Monster Compendium
Thesis Stage: Concept, Research, Prototype Hell
I'll probably figure out the rules during playtest... Goal, Player Levels, and Room randomization can work like Munchkin... turn-based gameplay between monsters and players, like in Slay the Spire...
Basic card set includes:
Action Cards (Attack and Defense)
Boosted Action Cards (Attack and Defense)
Magic Potion Card (+1 Level)
Monster Specific Action Cards
Monster Cards with various levels and traits
Empty Dungeon Cards
Curse Cards (-1 Level)
Equitable treasure cards
I should probably make a few more monster variations and monster-oriented cards (Treasure that only reacts to specific monsters, cards to declaw or turn a monster to your side or towards another player) and ways to sabotage other players if the PVP element becomes more relevant. Classes/Race cards can also be explored, toned down, maybe set for each run, but still variable to create different combos.
I want to add another element, especially for a solo variation. Most games add progression tracking through a game map, additionally adding an element of choice and/or exploration (Slay the Spire, Shroom and Gloom). I'll probably look into exploration and map elements anyways during the next prototype...
I can also do something more interesting for the enemy attack phase. "Undertale" turns into a bullet hell; "Munchkin" just throws it away entirely and power-scales.
Maybe a more narrative element outside exploration can be added, though... maybe you can create the creatures you fight... like that one <---
Farms can always be added if you try hard enough :)