Showdown of the Skalds + Crystalline Crawler + Kor Skyfisher + Conclave Mentor

Showdown of the Skalds

Crystalline Crawler

Kor Skyfisher

Conclave Mentor

How it works

1. Cast Kor Skyfisher, 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. Kor Skyfisher triggers, returning itself to your hand.
4. Repeat.