Heartmender + Yahenni, Undying Partisan + Hardened Academic

Heartmender

Yahenni, Undying Partisan

Hardened Academic

How it works

1. Activate Yahenni by sacrificing Heartmender.
2. When Heartmender dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Hardened Academic triggers, putting a +1/+1 counter on Heartmender.
4. Resolve the Yahenni ability.
5. Repeat.

This clever loop turns Yahenni, Undying Partisan's sacrifice outlet into an engine by feeding it Heartmender over and over again. Each time Heartmender perishes, its persist ability normally returns it to the battlefield with a dreaded -1/-1 counter, but Hardened Academic cleverly steps in to immediately neutralize that drawback by placing a +1/+1 counter on it whenever a card leaves your graveyard. Because +1/+1 and -1/-1 counters annihilate each other instantly as a state-based action, Heartmender is left completely clean and ready to be sacrificed to Yahenni once more. To top it all off, Heartmender's own upkeep trigger even clears away any lingering counters on its own, ensuring this cycle of endless resurrections, deaths, and triggers keeps running smoothly.