Play Gruul Turf. When it enters, Amulet of Vigor, Gruul Turf and Springheart Nantuko trigger.
Resolve the Amulet of Vigor trigger, untapping Gruul Turf.
Holding priority, activate Gruul Turf by tapping it, adding .
Resolve the Gruul Turf trigger, returning it from the battlefield to your hand.
Resolve the Springheart Nantuko trigger, causing you to pay 1 to create a token copy of Wayward Swordtooth.
Because of the additional Wayward Swordtooth token, you can play an additional land this turn.
Repeat.
This clever loop relies on Gruul Turf's bounce trigger to continuously recast the land, while Amulet of Vigor bypasses the usual tempo penalty by instantly untapping it upon entry. With the mana generated from tapping the returning land before it bounces, you can easily pay for Springheart Nantuko's landfall ability to repeatedly clone creatures. Meanwhile, Wayward Swordtooth provides the crucial extra land drop needed to keep replaying the Gruul Turf over and over again, resulting in an infinite army of copies.