Murder at Castle Nathria Cards List & Guide
Unlike predetermined starting decks in actual PvE dungeon runs, in duels you build your starting deck, and continue as a PvP dungeon run.
Too bad they don't remake dungeon runs, the last one was incredibly fun, actually IS, I still do those sometimes.
Calling Mercs whatever this failure of a mode is supposed to be, is an insult to dungeon runs and any roguelike adventures. And to think they charge money for that and people actually P2W this horror.