Sister Hospitaller, Yahenni, Undying Partisan, and Fiend Hunter

Prerequisites

• Sister Hospitaller on the battlefield
• Yahenni, Undying Partisan on the battlefield
• Fiend Hunter in hand
• available

Steps

1. Cast Fiend Hunter by paying its mana cost
2. When Fiend Hunter enters, its first ability triggers, exiling Sister Hospitaller
3. Activate Yahenni by sacrificing Fiend Hunter
4. When Fiend Hunter dies, its second ability triggers, returning Sister Hospitaller from exile to the battlefield
5. When Sister Hospitaller enters, it triggers, returning Fiend Hunter from your graveyard to the battlefield
6. When Fiend Hunter enters, its first ability triggers, exiling Sister Hospitaller
7. Resolve the Yahenni ability
8. Repeat from step 3

Results

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