The Thunderstone is the main objective for each game session. It acts as both a source of Victory Points (VP) as well as being the end-game condition.
The game ends when one of the following occurs.
- The Thunderstone is pushed into the first rank and no one claims it. This typically occurs through failure to defeat the first rank monster, or by using Banish or the Elf/Thyrian hero's respective abilities.
- A player defeats the first rank monster and the Thunderstone was in the second rank. That player then claims the Thunderstone and adds it to their discard pile. This is the only method by which the Thunderstone can be claimed.
There are multiple Thunderstones, such as the Stone of Mystery in the base set and the Stone of Agony in the WotE expansion, and one of these is chosen to be included in the bottom 10 cards of the dungeon deck.
Some other Thunderstones may also provide bonuses to the player who reveals it, or has it as a part of their deck when using certain game variants.