Xavier Sal, Infested Captain + Haunted One + Hyrax Tower Scout + Altar of Dementia

Xavier Sal, Infested Captain

Haunted One

Hyrax Tower Scout

Altar of Dementia

How it works

1. Activate Xavier Sal's first ability by tapping it and removing a +1/+1 counter from Hyrax Tower Scout if it has one, or any counter from another permanent you control otherwise.
2. Xavier Sal triggers, causing it and all other creatures you control that share a creature type with it to get +2/+0 and gain undying until end of turn.
3. Resolve the Xavier Sal ability, causing you to populate.
4. Activate Altar of Dementia by sacrificing Hyrax Tower Scout.
5. When Hyrax Tower Scout dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. When Hyrax Tower Scout enters the battlefield, it triggers, untapping Xavier Sal.
7. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Hyrax Tower Scout's power.
8. Repeat.

This clever loop lets you grind an opponent's library down to dust by continuously recycling your own crew through the graveyard. The engine hums when Haunted One grants your Commander—in this case, Xavier Sal, Infested Captain—and your fellow creatures undying the moment they become tapped. You send Hyrax Tower Scout to the yard via Altar of Dementia to mill your target, and its undying trigger immediately brings it right back with a +1/+1 counter. As the Scout re-enters, its triggered ability untaps Xavier Sal to restart the process while also triggering the Captain's stat boost, letting you endlessly repeat the cycle of sacrifice, resurrection, and untapping.