Xavier Sal, Infested Captain + Intruder Alarm + Yotian Dissident

Xavier Sal, Infested Captain

Intruder Alarm

Yotian Dissident

How it works

1. Activate Xavier Sal by tapping it and removing a counter from a permanent you control, creating a copy of an artifact creature token you control.
2. When the creature token enters the battlefield, Intruder Alarm and Yotian Dissident trigger.
3. Resolve the Intruder Alarm trigger, untapping all creatures.
4. Resolve the Yotian Dissident trigger, putting a counter on it.
5. Repeat.

This ingenious little engine relies on Xavier Sal, Infested Captain to steadily pump out copies of an artifact creature token by spending a counter from another permanent. Every time that new token hits the board, Intruder Alarm springs into action to untap all creatures—including Xavier Sal—while Yotian Dissident feeds the loop by placing a fresh +1/+1 counter back onto a creature you control. Because that newly placed counter instantly replenishes the cost required for Xavier Sal, Infested Captain to activate again, you create an endless feedback loop of creature tokens, entering-the-battlefield triggers, and untaps.