Basri's Lieutenant, Cathars' Crusade, and Altar of Dementia

Prerequisites

• Basri's Lieutenant on the battlefield
• Cathars' Crusade on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing a creature with at least one +1/+1 counter
2. Basri's Lieutenant trigger, creating a 2/2 Knight token
3. When Knight token enters the battlefield, Cathars' Crusade triggers, putting a +1/+1 counter on each creature you control
4. Resolve the Altar of Dementia ability, causing target player to mill cards equal to the sacrificed creature's power
5. Repeat

Results

• Infinite +1/+1 counters
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers