Athreos, Shroud-Veiled + Enduring Bondwarden + Umbral Collar Zealot Combo

All permanents on the battlefield.

You control at least one other nontoken creature. Enduring Bondwarden has at least one coin counter on it.

Activate Umbral Collar Zealot by sacrificing Enduring Bondwarden.

When Enduring Bondwarden dies, it and Athreos' third ability trigger.

Resolve the Enduring Bondwarden trigger, putting all counters from it onto another nontoken creature you control.

Resolve the Athreos trigger, returning Enduring Bondwarden from your graveyard to the battlefield.

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.

Resolve the Umbral Collar Zealot ability from step 1.

Activate Umbral Collar Zealot by sacrificing the nontoken creature with a coin counter on it, adding one mana of any color.

When the creature dies, its ability from Enduring Bondwarden and Athreos' third ability trigger.

Resolve the creature's trigger, putting all counters from it onto Enduring Bondwarden.

Resolve the Athreos trigger, returning the creature from your graveyard to the battlefield.

Repeat.

Infinite +1/+1 counters on a creature

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Infinite death triggers

Infinite surveil