Animate a Forest that enters untapped using Kamahl's Will
Cast Springheart Nantuko for its bestow cost by paying 1, attaching it to the animated Forest.
Play a land. When the land enters, Springheart Nantuko triggers, causing you to pay 1 to create two token copies of the Forest that enters untapped.
When the Forest tokens enter, Springheart Nantuko triggers twice.
Holding priority, activate the Forest tokens by tapping them, adding .
Resolve the first Springheart Nantuko trigger, choosing not to pay and creating two 1/1 Insect creature tokens.
Resolve the second Springheart Nantuko trigger, causing you to pay 1 to create two token copies of the Forest that enters untapped.
Repeat from step 4.
This charming loop transforms a simple land drop into an exponential cascade of mana and creatures by turning a land into an active participant. You begin by casting Kamahl's Will to animate your lands, allowing you to bestow Springheart Nantuko directly onto a living Forest so it can ride along as a creature. When you play a subsequent land, the Nantuko's landfall ability triggers to copy that animated Forest, an effect brilliantly doubled by Elspeth, Storm Slayer's static replacement ability that supercharges your token generation. By tapping your newly minted Forest tokens for mana before paying to repeat the process, the loop is completely mana-neutral, leaving you with an overwhelming army of lands, insects, and infinite triggers.