Umbral Collar Zealot, and Thran Vigil

Prerequisites

• Umbral Collar Zealot on the battlefield
• Thran Vigil on the battlefield

Steps

1. Activate Umbral Collar Zealot by sacrificing the creature with persist
2. When that creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Thran Vigil triggers, putting a +1/+1 counter on that creature
4. Remove a +1/+1 counter and a -1/-1 counter from that creature as a state-based action
5. Resolve the Umbral Collar Zealot ability from step 1
6. Repeat

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite surveil