Cavalier of Night, Activated Sleeper, and Umbral Collar Zealot

Prerequisites

• Cavalier of Night on the battlefield
• Activated Sleeper in the graveyard
• Umbral Collar Zealot on the battlefield

Steps

1. Activate Umbral Collar Zealot by sacrificing Cavalier of Night
2. When Cavalier of Night dies, it triggers, returning Activated Sleeper from your graveyard to the battlefield as a copy of Cavalier of Night
3. When Activated Sleeper enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature
4. Resolve the Umbral Collar Zealot ability from step 1
5. Activate Umbral Collar Zealot by sacrificing Activated Sleeper
6. When Activated Sleeper dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night
7. When Activated Sleeper enters the battlefield, it triggers; choose not to sacrifice a creature
8. Resolve the Umbral Collar Zealot ability from step 5
9. Repeat from step 5

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite surveil 1