Medomai the Ageless + Capsize + Lignify

Steps

1. Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
2. Move to your next turn.
3. Cast Lignify by paying its mana cost, attaching it to Medomai and causing it to lose its abilities.
4. Declare Medomai as an attacker.
5. Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Lignify and Capsize to your hand.
6. Repeat from step 1.