Phantom Steed, Karmic Guide, and Ashnod's Altar

Prerequisites

• Phantom Steed on the battlefield
• Karmic Guide in exile
• Ashnod's Altar on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Phantom Steed, adding
2. Phantom Steed leaves the battlefield, returning Karmic Guide from exile to the battlefield
3. Karmic Guide enters the battlefield, returning Phantom Steed from your graveyard to the battlefield
4. Phantom Steed enters the battlefield, exiling Karmic Guide until Phantom Steed leaves the battlefield
5. Repeat

Results

• Infinite colorless mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers