Athreos, Shroud-Veiled, Enduring Bondwarden, and Yahenni, Undying Partisan

Prerequisites

• Athreos, Shroud-Veiled on the battlefield
• Enduring Bondwarden on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Enduring Bondwarden
2. When Enduring Bondwarden dies, it and Athreos' third ability trigger
3. Resolve the Enduring Bondwarden trigger, putting all counters from it onto another nontoken creature you control
4. Resolve the Athreos trigger, returning Enduring Bondwarden from your graveyard to the battlefield
5. When Enduring Bondwarden enters the battlefield, its backup ability triggers, putting a +1/+1 counter on the creature who had a coin counter placed on it, and giving it the printed ability until end of turn
6. Resolve the Yahenni ability from step 1
7. Activate Yahenni by sacrificing the nontoken creature with a coin counter on it, adding one mana of any color
8. When the creature dies, its ability from Enduring Bondwarden and Athreos' third ability trigger
9. Resolve the creature's trigger, putting all counters from it onto Enduring Bondwarden
10. Resolve the Athreos trigger, returning the creature from your graveyard to the battlefield
11. Repeat

Results

• Infinite +1/+1 counters on a creature
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers