Dungeon World: World of Dungeons!
The ultimate weapon given to Tiwaz Vault by the Old Gods
Every dwarven vault was given an ultimate weapon by the Old Gods, so that if it came to it, the dwarves would never be overcome, even as the gods destroyed the world.
He is the Righteous One, wrapped in the Armor Imperishable, armed with the rune-chains of every oath the dwarves have kept. Awakened only in the greatest need, and none can overcome him.