Ashnod's Altar + Fiend Hunter + Karmic Guide

Ashnod's Altar

Fiend Hunter

Karmic Guide

How it works

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