Xavier Sal, Infested Captain, Haunted One, Hyrax Tower Scout, and Yahenni, Undying Partisan

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Haunted One on the battlefield
• Hyrax Tower Scout on the battlefield
• Yahenni, Undying Partisan on the battlefield
• There is at least one counter on a permanent you control except Xavier Sal
• Xavier Sal does not have summoning sickness
• Hyrax Tower Scout has no more than one +1/+1 counter on it

Steps

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 Yahenni 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 Yahenni ability
8. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite copies of creature tokens you control
• Infinitely powerful Humans, Fungi and Pirates you control until end of turn except Hyrax Tower Scout