The Brothers’ War introduces a large suite of combo enablers. This article collects 22 infinite or game-winning combos involving one or more new cards (ordered by format).
Although some may make a splash on competitive formats, the vast majority of these combos are not going to lead to tournament-winning decks. But that’s not the goal. They’re just plain fun to imagine, and they could lead to sweet casual jank brewing. Also, all of them use single copies of any card, so assuming you use a Commander with the right color identity, all of the Pioneer/Modern/etc. combos are viable in Commander as well.
Urza, Prince of Kroog (Limited)
With Urza, spend six mana to make a copy of Su-Chi Cave Guard. Next, spend one mana and sacrifice the copy to Penregon Strongbull. The dying Su-Chi Cave Guard adds eight mana, so each loop nets one mana and deals one damage to each opponent. Repeat as often as you like to win the game.