Xavier Sal, Infested Captain | Haunted One | Thornbite Staff

(and one other card)

There is at least one counter on a permanent you control except
Xavier Sal.
Xavier Sal does not have summoning sickness.
Thornbite Staff attached to
Xavier Sal.
You control at least one additional nontoken Human, Fungus and/or Pirate that has no more than one +1/+1 counter on it.

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.
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.
Resolve the
Xavier Sal ability, causing you to populate.
Activate
Phyrexian Altar by sacrificing the additional Human, Fungus and/or Pirate, adding one mana of any color.
When the creature dies, its undying ability and
Xavier Sal trigger.
Resolve the creature's undying trigger, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Xavier Sal trigger, untapping it.
Repeat.