Karlach, Fury of Avernus
Extra combat steps in red usually come with a bill: haste on the new attackers, a body that dies to the next blocker, a payoff that only lands if you've committed the board first. Here the sequencing runs the other way. The trigger fires when you swing in the first combat phase, untaps the attackers, and hands them first strike before combat damage resolves, so the creatures are far likelier to survive the initial exchange and be ready to go again when the additional combat phase arrives. That untap is the load-bearing clause: it means the extra phase isn't a fresh set of attackers you have to build toward, it's the same board hitting twice, with vigilance stapled on for the turn. The Choose a Background line is what turns this from a fixed 5/4 into a construction toolkit; the second command-zone slot lets the multiplied-swing engine borrow keywords, protection, or evasion it doesn't natively bring, so the same untap-and-repeat frame can be pointed at trample, menace, or damage-doubling depending on which Background rides shotgun. Red has printed additional-combat effects since its earliest years, but most treated the extra phase as a tempo gamble; the design instinct here is to remove the risk from the attack step and let a modular partner supply the reach.
