Sister Hospitaller, Phantom Steed, and Yahenni, Undying Partisan

Prerequisites

• Sister Hospitaller in hand
• Phantom Steed in the graveyard
• Yahenni, Undying Partisan on the battlefield
• available

Steps

1. Cast Sister Hospitaller by paying
2. When Sister Hospitaller enters, it triggers, returning Phantom Steed from your graveyard to the battlefield and causing you to gain life equal to its mana value
3. When Phantom Steed enters, it triggers, exiling Sister Hospitaller until Phantom Steed leaves the battlefield
4. Activate Yahenni by sacrificing Phantom Steed
5. When Phantom Steed leaves the battlefield, Sister Hospitaller is returned from exile to the battlefield
6. Repeat from step 2
7. Resolve all Yahenni abilities

Results

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