Activate Selvala by paying and tapping it, adding at least 1.
Activate Shilgengar 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 loop uses Shilgengar, Sire of Famine as a grim engine to recycle your graveyard, letting you sacrifice Selvala, Heart of the Wilds and Slimefoot and Squee to generate Blood tokens. You then use Slimefoot and Squee's resurrection ability—fueled by the massive mana boost from Selvala's tap—alongside the Saproling token generated upon its re-entry to fuel the loop anew. While Frostcliff Siege sits quietly on the battlefield, its chosen Temur or Jeskai modes can take advantage of the chaos, though the core of the combo relies purely on this self-sustaining sacrifice and revival cycle.