Wormfang Manta + Torpor Orb + Ilharg, the Raze-Boar

Wormfang Manta

Torpor Orb

Ilharg, the Raze-Boar

How it works

1. Attack with Ilharg.
2. Ilharg's attack trigger triggers, putting Wormfang Manta onto the battlefield tapped and attacking.
3. At the beginning of your end step, Wormfang Manta is returned to your hand.
4. This triggers its LTB, granting you an extra turn after this one.
5. Repeat for infinite turns.