Felidar Guardian, Liliana, Death's Majesty, and Altar of Dementia

Prerequisites

• Felidar Guardian on the battlefield
• Liliana, Death's Majesty on the battlefield
• Altar of Dementia on the battlefield
• Liliana has at least four loyalty counters on it

Steps

1. Activate Altar of Dementia by sacrificing Felidar Guardian, causing target player to mill cards equal to Felidar Guardian's power
2. Activate Liliana's second loyalty ability by removing three loyalty counters from it, returning Felidar Guardian from your graveyard to the battlefield
3. Felidar Guardian enters the battlefield, blinking Liliana
4. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill