Emeria Shepherd, Felidar Guardian, and Ashnod's Altar

Prerequisites

• Emeria Shepherd on the battlefield
• Felidar Guardian in hand
• Ashnod's Altar on the battlefield
• available

Steps

1. Cast Felidar Guardian by paying
2. Felidar Guardian enters the battlefield, blinking Plains
3. Emeria Shepherd triggers
4. Holding priority, activate Ashnod's Altar by sacrificing Felidar Guardian, adding
5. Resolve the Emeria Shepherd trigger, returning Felidar Guardian from your graveyard to the battlefield
6. Repeat from step 2

Results

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