Play a land. When the land enters, Springheart Nantuko triggers, causing you to pay 1 to create a token copy of Dryad Arbor.
When the Dryad Arbor token enters, Springheart Nantuko triggers. Holding priority, activate the Dryad Arbor token by tapping it, adding .
Zhur-Taa Ancient triggers, adding .
Resolve the Springheart Nantuko trigger, causing you to pay 1 to create a token copy of Dryad Arbor.
Repeat from step 2.
This clever loop uses Springheart Nantuko bestowed onto Dryad Arbor to spin out an endless sea of land-creature tokens whenever you make a land drop. Because the resulting token copies are also lands, each new Dryad Arbor entry triggers Springheart Nantuko anew while simultaneously feeding the mana engine. Zhur-Taa Ancient doubles every drop of mana generated by tapping those lands, effortlessly sustaining the {1}{G} cost required to keep the cycle going. Meanwhile, The Fire Crystal sits on the sidelines granting your creatures haste, ensuring that your massive swarm of tokens is immediately ready to overwhelm the table.