Necroduality + Rot Hulk + Umbral Collar Zealot

Necroduality

Rot Hulk

Umbral Collar Zealot

How it works

1. Cast Rot Hulk by paying 5.
2. When Rot Hulk enters, it and Necroduality trigger.
3. Holding priority, activate Umbral Collar Zealot by sacrificing Rot Hulk.
4. Resolve the Rot Hulk trigger, failing to return anything to the battlefield.
5. Resolve the Necroduality trigger, creating a token copy of Rot Hulk.
6. When the token Rot Hulk enters, it triggers, returning Rot Hulk from your graveyard to the battlefield.
7. Repeat from step 2.

This elegant undead engine centers around the recursive loop enabled by Rot Hulk and Necroduality. As the original Rot Hulk enters the battlefield, Necroduality jumps in to create a token copy of it, and you can immediately sacrifice the original to Umbral Collar Zealot to bin it and trigger a surveil. When the token Rot Hulk enters, its own ability targets the original Rot Hulk in your graveyard, bringing it right back to the battlefield to restart the cycle. This creates an endless loop of coming-and-going corpses, fueling infinite enters-the-battlefield triggers, death triggers, token copies, and endless surveils through Umbral Collar Zealot's sacrifice outlet.