Phyrexian Altar + Fiend Hunter + Angel of Indemnity

Phyrexian Altar

Fiend Hunter

Angel of Indemnity

How it works

1. Cast Fiend Hunter by paying its mana cost.
2. When Fiend Hunter enters, its first ability triggers, exiling Angel of Indemnity.
3. Activate Phyrexian Altar by sacrificing Fiend Hunter.
4. When Fiend Hunter dies, its second ability triggers, returning Angel of Indemnity from exile to the battlefield.
5. When Angel of Indemnity enters, it triggers, returning Fiend Hunter from your graveyard to the battlefield.
6. When Fiend Hunter enters, its first ability triggers, exiling Angel of Indemnity.
7. Repeat from step 3.