Thunderstone: Heart of Doom

From BoardGameGeek:

"Thunderstone: Heart of Doom brings the struggle introduced in Thunderstone to an epic climax. This expansion adds seven heroes, thirteen village cards, five monster groups, one treasure set, three settings, three guardians and one thunderstone.

No new rules or mechanisms are added in Thunderstone: Heart of Doom, but the many unique card abilities add and change typical deck-building strategies. Notable additions include cards that enable the obtaining of heroes and items while in the dungeon (including the Village Cutpurse, Gem Treasures and Highland Captain), monsters that add additional ranks to the dungeon (Dryads) and the Doppleganger monsters, which imitate villagers and mercenaries, with potentially deadly results!

Additionally, players can fight the final battle to seal the rift and save the world, with the "Rite of Banishing" setting that pits them against the incredibly powerful "Heart of Doom" guardian."