Primo, the Unbounded + Breath of Fury + Fervor

Primo, the Unbounded

Breath of Fury

Fervor

How it works

1. Deal combat damage to an opponent using the creature that has Breath of Fury attached, triggering Breath of Fury and Primo.
2. Resolve the Primo trigger, creating a 0/0 Fractal creature token that enters with a number of +1/+1 counters on it equal to the damage dealt.
3. Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to and attach it to the Fractal token, then causing you to untap all creatures you control and to get an additional combat phase after this one.
4. Repeat each combat phase.

This loop transforms a single successful swing into an endless chain of extra combat steps, fueled entirely by combat damage and token generation. When your creature enchanted with Breath of Fury connects with an opponent, Primo, the Unbounded triggers off the base-zero power combat damage to spawn a massive Fractal token whose counters match the damage dealt. At the same time, Breath of Fury forces you to sacrifice the original attacker, but smoothly relocates itself onto the freshly minted Fractal so the process can begin anew. Meanwhile, Fervor ensures that your newly created token doesn't have to wait around to attack, granting the haste it needs to immediately swing away in the additional combat phase generated by Breath of Fury.