Showdown of the Skalds + Crystalline Crawler + Horned Kavu + Primal Vigor

Showdown of the Skalds

Crystalline Crawler

Horned Kavu

Primal Vigor

How it works

1. Cast Horned Kavu, putting 2 +1/+1 counter on Crystalline Crawler with Showdown of the Skalds.
2. Remove 2 +1/+1 counter from Crystalline Crawler to add .
3. Horned Kavu triggers, returning itself to your hand.
4. Repeat.