Umbral Collar Zealot + Dualcaster Mage + Black Sun's Twilight

Umbral Collar Zealot

Dualcaster Mage

Black Sun's Twilight

How it works

1. Cast Black Sun's Twilight by paying 5
2. Holding priority, cast Dualcaster Mage by paying its mana cost.
3. When Dualcaster Mage enters, it triggers, targeting Black Sun's Twilight.
4. Holding priority, activate Umbral Collar Zealot by sacrificing Dualcaster Mage.
5. Resolve the Dualcaster Mage trigger, copying Black Sun's Twilight
6. Resolve the Black Sun's Twilight copy, returning Dualcaster Mage from your graveyard to the battlefield.
7. Repeat from step 3.

This loop sets up an infinite recursion using Dualcaster Mage and Black Sun's Twilight, fueled by a clever sacrifice outlet. By casting Black Sun's Twilight with an X of 5 or more and responding with Dualcaster Mage, you can copy the spell to target itself or your graveyard recursion, allowing you to continually bring back the Mage each time it is sacrificed. The Umbral Collar Zealot serves as the vital sacrifice engine that makes this loop repeatable, letting you instantly sacrifice Dualcaster Mage to its ability and triggering its surveillance effect along the way.