Errant, Street Artist + Reality Spasm + Insidious Will

Errant, Street Artist

Reality Spasm

Insidious Will

How it works

1. Cast Reality Spasm by paying at least 3, targeting at least three permanents and choosing the untap mode.
2. Holding priority, cast Insidious Will by paying its mana cost, copying Reality Spasm, targeting at least three permanents.
3. Holding priority, activate at least two mana-producing permanents you control by tapping them, adding at least 1.
4. Activate Errant by paying 1 and tapping it, copying the Reality Spasm copy, targeting Errant and at least two mana-producing permanents you control.
5. Resolve the copy of Reality Spasm from step 3, untapping Errant and at least two mana-producing permanents you control.
6. Repeat from step 3.

This intricate loop relies on copying and recopying a single copied spell to generate an endless cascade of mana and triggers. By casting Reality Spasm with a large enough $X$ value, you set the foundation for your permanents to untap. Insidious Will steps in early to duplicate that spell on the stack, giving you a copy to manipulate. From there, Errant, Street Artist does the heavy lifting by repeatedly tapping to copy that active copy of Reality Spasm, targeting both Errant itself and your mana producers so they can reset and fund the next iteration.