Xavier Sal, Infested Captain + Haunted One + Thornbite Staff + Umbral Collar Zealot

Xavier Sal, Infested Captain

Haunted One

Thornbite Staff

Umbral Collar Zealot

How it works

1. Activate Xavier Sal's first ability by tapping it and removing a +1/+1 counter from the additional nontoken Human, Fungus and/or Pirate 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 Umbral Collar Zealot by sacrificing the additional Human, Fungus and/or Pirate.
5. When the creature dies, its undying ability and Xavier Sal trigger.
6. Resolve the creature's undying trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
7. Resolve the Xavier Sal trigger, untapping it.
8. Resolve the Umbral Collar Zealot ability, putting a +1/+1 counter on it.
9. Repeat.

This clever engine centers around Xavier Sal, Infested Captain—equipped with Thornbite Staff to give it a ranged tap ability and a way to untap whenever a creature dies—and a shared creature type backed by Haunted One's triggered grant of undying. You tap Xavier Sal to strip a counter and populate, then sacrifice a creature to Umbral Collar Zealot, which triggers both the Staff to untap Xavier Sal and Haunted One to return the sacrificed creature via undying with a fresh +1/+1 counter. Because Thornbite Staff also attaches itself when a Shaman enters, you can easily cycle your creatures back and forth to continuously fuel Umbral Collar Zealot's sacrifices while looping your board state indefinitely.