It is a singleton format, meaning you can only play one copy of a card in your 99-card deck (excluding basic lands) and your commander that is outside the main deck
It generated its share of debate on just how good (or not) that it might be
If youve given Gabriel rampage 3, you can swing at your opponent with the widest board and watch your commander become massive and likely clear out their creatures
The card makes for a very fun win condition that can also go in the Command Zone

Rhys the Redeemed -- Commander | Stephen Johnson Creatures (21) 1 Arbor Elf 1 Avacyn, Angel of Hope 1 Avacyn's Pilgrim 1 Avenger of Zendikar 1 Bramblewood Paragon 1 Champion of Lambholt 1 Craterhoof Behemoth 1 Dragonlord Dromoka 1 Druid of the Cowl 1 Grand Abolisher 1 Imperious Perfect 1 Jagged-Scar Archers 1 Jazal Goldmane 1 Leaf Gilder 1 Mirror Entity 1 Regal Force 1 Seedborn Muse 1 Seeker of Skybreak 1 Spawnwrithe 1 Voyaging Satyr 1 Wellwisher Planeswalkers (1) 1 Huatli, Radiant Champion Instants (5) 1 Harrow 1 Rootborn Defenses 1 Seedtime 1 Swords to Plowshares 1 Teferi's Protection Sorceries (11) 1 Cultivate 1 Fumigate 1 Harmonize 1 Rampant Growth 1 Rout 1 Shamanic Revelation 1 Slaughter the Strong 1 Tempt with Discovery 1 Tooth and Nail 1 Triumph of the Hordes 1 Wrath of God Enchantments (13) 1 Anointed Procession 1 Beastmaster Ascension 1 Concordant Crossroads 1 Darksteel Mutation 1 Doubling Season 1 Ghostly Prison 1 Instill Energy 1 Lignify 1 Parallel Lives 1 Presence of Gond 1 Privileged Position 1 Sandwurm Convergence 1 Zendikar Resurgent

[4] During gameplay, the player must defeat eight Club Masters, each with a different deck representing one of the game's elemental card types