Activate Selvala by paying and tapping it, adding at least 1.
Activate Umbral Collar Zealot twice by sacrificing Selvala and Slimefoot and Squee.
Activate Slimefoot and Squee by paying 1 and sacrificing a Saproling, returning it and Selvala from your graveyard to the battlefield.
When Slimefoot and Squee enters the battlefield, it triggers, creating a 1/1 Saproling creature token.
Repeat.
This ingenious loop turns the graveyard into a bustling workshop, fueled by the legendary power of Selvala, Heart of the Wilds to generate a massive surplus of colored mana. Thanks to Rising of the Day granting haste, Selvala and Slimefoot and Squee can be repeatedly sacrificed to Umbral Collar Zealot's activation, which effortlessly fills your graveyard while sifting through your library. Then, Slimefoot and Squee uses that accumulated mana and a freshly minted Saproling token to resurrect itself and Selvala, restarting the entire cycle and instantly triggering a brand new token to keep the engine running.