Game description from the publisher:
Following on the heels of Thunderstone Advance: Caverns of Bane, Thunderstone emerges into the deepest trouble yet. The tunnels under the fortress at Cheah Dell are clear. The lost dwarven kingdom of Caligin is reclaimed. And the djinni lich, Mowtil, has been defeated, sealing the portal of black flame into Tala. The adventurers have collected three more Thunderstones, and Doom's full plans are revealed. He has corrupted the heart of Tala, Dun Ordha. A monstrous army marches on the capital city, even as the final Thunderstone is revealed to be held by King Caelan himself. Can the adventurers race ahead of an army to save the city from a siege outside the walls and sickly corruption within?
Thunderstone Advance: Root of Corruption, the second expansion for Thunderstone Advance, introduces new challenges and an all-new way to play: co-op! It also features ruinous sin incarnates, vicious scavenger gnolls, thrall summoners to bring back memorable foes, seven new heroes, six new monster groups, fifteen new village cards, and a new poster map board that creates options for co-op play using existing cards and rules! What's more, all Ambusher cards from Towers of Ruin and Caverns of Bane have been reprinted with updated graphics to increase visibility.