Xavier Sal, Infested Captain + Intruder Alarm + Serra Redeemer

Xavier Sal, Infested Captain

Intruder Alarm

Serra Redeemer

How it works

1. Activate Xavier Sal by tapping it and removing a counter from a permanent you control, creating a copy of a creature token you control with base power 2 or less.
2. When the creature token enters the battlefield, Intruder Alarm and Serra Redeemer trigger.
3. Resolve the Intruder Alarm trigger, untapping all creatures.
4. Resolve the Serra Redeemer trigger, putting two +1/+1 counters on the creature token.
5. Repeat.

This ingenious loop hinges on Xavier Sal, Infested Captain using a counter to populate a small creature token, which immediately brings Serra Redeemer into the equation to hand out a pair of fresh +1/+1 counters to the newcomer. That very same entry triggers Intruder Alarm, standing ready to untap all creatures—including Xavier Sal, Infested Captain itself—so you can tap it right back to repeat the cycle. Because the token enters with power 2 or less to satisfy Serra Redeemer, and every iteration resets your untap catalyst via Intruder Alarm while feeding counters back into Xavier Sal, Infested Captain's upkeep cost, you get an unstoppable cascade of token copies and creature untaps.