Basri's Lieutenant, Cathars' Crusade, and Phyrexian Altar

Prerequisites

• Basri's Lieutenant on the battlefield
• Cathars' Crusade on the battlefield
• Phyrexian Altar on the battlefield
• You control at least one additional creature with at least one +1/+1 counter

Steps

1. Activate Phyrexian Altar by sacrificing a creature with at least one +1/+1 counter, adding one mana of any color
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. Repeat

Results

• Infinite +1/+1 counters
• Infinite colored mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers