Yedora, Grave Gardener, Ashnod's Altar, and Den Protector

Prerequisites

• Yedora, Grave Gardener on the battlefield
• Ashnod's Altar on the battlefield
• Den Protector on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Den Protector, adding
2. When Den Protector dies, Yedora triggers, returning Den Protector from your graveyard to the battlefield face down as a Forest land
3. Activate Den Protector by tapping it, adding
4. Activate Den Protector's megamorph ability by paying , turning it face up
5. Den Protector triggers, returning any card from your graveyard to your hand
6. Repeat

Results

• Infinite colorless mana
• Infinite death triggers
• Infinite landfall triggers
• Infinite LTB
• Infinite sacrifice triggers
• Return all cards from your graveyard to your hand