Xavier Sal, Infested Captain + Intruder Alarm + Tribute to the World Tree

Xavier Sal, Infested Captain

Intruder Alarm

Tribute to the World Tree

How it works

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

This elegant loop turns Xavier Sal, Infested Captain into a relentless token-copying engine by leaning on Intruder Alarm to untap him each time a new copy arrives. Because the populated tokens enter with a base power of 2 or less, Tribute to the World Tree triggers to place two +1/+1 counters on them, supplying the very counters you need to pay for Xavier Sal's populate ability again.