1Cast Capture of Jingzhou by paying , causing you to take an extra turn after this one.
2At the beginning of your combat phase, Helm of the Host triggers, creating a token copy of Izzet Chemister.
3Activate the Izzet Chemister token's first ability by paying and tapping it, exiling Capture of Jingzhou from your graveyard.
4On your next turn, activate the Izzet Chemister token's last ability by paying , tapping it, and sacrificing it, casting the exiled spell without paying its mana cost.
5Resolve that spell, causing you to take an extra turn after this one.