Puppeteer Clique + Umbral Collar Zealot + Hardened Academic

Puppeteer Clique

Umbral Collar Zealot

Hardened Academic

How it works

1. Activate Umbral Collar Zealot by sacrificing Puppeteer Clique.
2. When Puppeteer Clique dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Hardened Academic and Puppeteer Clique trigger.
4. Resolve the Hardened Academic trigger, putting a +1/+1 counter on Puppeteer Clique.
5. Resolve the Puppeteer Clique trigger, allowing you to put a creature card from an opponent's graveyard onto the battlefield under your control.
6. Resolve the Umbral Collar Zealot ability
7. Repeat.