Stalwart Successor, Twilight Shepherd, and Yahenni, Undying Partisan

Prerequisites

• Stalwart Successor on the battlefield
• Twilight Shepherd on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Twilight Shepherd When Twilight Shepherd dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
2. When Twilight Shepherd enters, Stalwart Successor triggers, putting a +1/+1 counter on Twilight Shepherd Resolve the Yahenni ability
3. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite sacrifice triggers