Showdown of the Skalds + Crystalline Crawler + Whitemane Lion + Winding Constrictor

Showdown of the Skalds

Crystalline Crawler

Whitemane Lion

Winding Constrictor

How it works

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