Cube to be drafted against a horde in games of three-headed hydra, one pack before each match to improve your deck. You will also gain improvements called boons which are to be drafted cooperatively between each match.

Horde Format Rules can be found here: https://mtg.fandom.com/wiki/Horde_Magic

Rules Changes:
Your deck must be 30 cards after round 1, 40 cards after round 2, and 50 cards after round 3.
Tempting Offer now says each other player rather than each opponent.