Wormfang Manta enters the battlefield, triggering itself.
In response, activate Erratic Portal by paying ({1} magic symbol) and tapping it, returning Wormfang Manta from the battlefield to your hand.
When Wormfang Manta leaves the battlefield, it triggers, causing you to take an extra turn after this one.
Activate Sundial of the Infinite by paying ({1} magic symbol) and tapping it, ending the turn and preventing Wormfang Manta's ETB ability from resolving.