Vault Assault
From Archon Arcana - The KeyForge Wiki
Vault Assault is an official multiplayer format for KeyForge. In Vault Assault, 3-5 players compete against each other in a race to forge three keys. The game also features a boon drafting round that is used to determine player order and to provide some unique game effects between rounds, giving players a chance to more interact with one another.
Full rules for Vault Assault are available from Ghost Galaxy. The boon cards are available as a print and play download or they can be purchased via ForgeFire Connect.