Errant, Street Artist + Reality Spasm + Doublecast

Prerequisites

You control at least two mana producing permanents, one of which can tap to produce at least {U}.

Steps

1. Cast Reality Spasm by paying at least {3}{U}{U}, targeting at least three permanents and choosing the untap mode.
2. Holding priority, cast Doublecast 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}{U}.
4. Activate Errant by paying {1}{U} 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.