Appa, Steadfast Guardian, Ashnod's Altar, and Necromancy

Prerequisites

• Appa, Steadfast Guardian in the graveyard
• Ashnod's Altar on the battlefield
• Necromancy in hand
• available

Steps

1. Cast Necromancy by paying its mana cost, returning Appa from your graveyard to the battlefield with Necromancy attached to it
2. When Appa enters, it triggers, airbending Necromancy
3. Necromancy triggers
4. Holding priority, cast Necromancy from exile due to its flash by paying
5. Appa triggers, creating a 1/1 Ally creature token
6. Activate Ashnod's Altar by sacrificing Appa, adding
7. Resolve Necromancy, returning Appa from your graveyard to the battlefield with Necromancy attached to it
8. Repeat from step 2

Results

• Infinite colorless mana
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite creature tokens
• Infinite death triggers
• Infinite storm count