Cast the creature in your hand by paying its mana cost.
Chulane triggers, causing you to draw a card and put Selesnya Sanctuary from your hand onto the battlefield untapped due to Spelunking.
When Selesnya Sanctuary enters, it and Retreat to Coralhelm trigger.
Holding priority, activate Selesnya Sanctuary by tapping it, adding due to Nyxbloom Ancient.
Resolve the Selesnya Sanctuary trigger, returning it from your hand to the battlefield.
Resolve the Retreat to Coralhelm trigger, untapping Chulane.
Resolve the creature spell cast in step 1.
Activate Chulane by paying 3 and tapping it, returning the creature from the battlefield to your hand.
Repeat.
This wondrous loop relies on the land-bouncing dance of Selesnya Sanctuary to repeatedly trigger the landfall ability of Retreat to Coralhelm, which untaps Chulane, Teller of Tales so you can bounce and recast your creatures indefinitely. Spelunking ensures that your returning bounce-lands enter the battlefield untapped and ready for action, completely bypassing their usual drawback. Meanwhile, Nyxbloom Ancient supercharges your economy by tripling the mana produced by tapping your lands, turning a modest land drop into an absolute gusher of green and white energy. As you churn through your deck, Chulane's triggered ability feeds you a steady stream of cards while smoothly assembling the rest of your infinite loop.