Heliod triggers, putting a +1/+1 counter on Scurry Oak.
Scurry Oak triggers, creating a creature token and an artifact token.
When the artifact token enters the battlefield, Pactdoll Terror triggers, causing you to gain life.
Repeat from step 2.
This delightful loop spins up by taking advantage of Heliod, Sun-Crowned's passive ability to react whenever you gain life by dropping a +1/+1 counter onto Scurry Oak. That counter stirs Scurry Oak into creating a Squirrel token, while Peregrin Took's replacement effect cleverly steps in to turn that event into *both* a creature token and an extra Food token. Because Pactdoll Terror watches artifacts enter the battlefield, that newly minted Food immediately drains your opponents and hands you life, which loops right back into Heliod, Sun-Crowned to keep the entire engine running infinitely.