Wormfang Manta + Erratic Portal + Sundial of the Infinite

Wormfang Manta

Erratic Portal

Sundial of the Infinite

How it works

1. Cast Wormfang Manta by paying 5.
2. Wormfang Manta enters the battlefield, triggering itself.
3. In response, activate Erratic Portal by paying 1 and tapping it, returning Wormfang Manta from the battlefield to your hand.
4. When Wormfang Manta leaves the battlefield, it triggers, causing you to take an extra turn after this one.
5. Activate Sundial of the Infinite by paying 1 and tapping it, ending the turn and preventing Wormfang Manta's ETB ability from resolving.
6. Repeat each turn.