Leonin Relic-Warder + Phyrexian Metamorph

Leonin Relic-Warder

Phyrexian Metamorph

How it works

1. Have Metamorph enter the battlefield, choosing to have it enter as Relic-Warder.
2. Target Metamorph with the copied Relic-Warder Trigger.
3. The Metamorph Relic-Warder exiles itself, then the second trigger returns it to the battlefield.
4. Repeat steps 1-3.

This clever loop relies on the continuous interaction between Leonin Relic-Warder and Phyrexian Metamorph copying it. As soon as Phyrexian Metamorph enters the battlefield as a copy of the first creature, its triggered ability goes on the stack and targets itself. When it is exiled and immediately returns, it triggers all over again, creating a self-sustaining cycle that generates infinite entry and leave-the-battlefield triggers for your permanents.