Sigarda's Summons, Bishop of Wings, Cathars' Crusade, and Phyrexian Altar

Prerequisites

• Sigarda's Summons on the battlefield
• Bishop of Wings on the battlefield
• Cathars' Crusade on the battlefield
• Phyrexian Altar on the battlefield
• You control an additional Angel

Steps

1. Activate Phyrexian Altar by sacrificing an Angel, adding one mana of any color
2. Bishop of Wings triggers, creating a 1/1 Spirit creature token
3. The Spirit enters the battlefield, triggering Cathars' Crusade, putting a +1/+1 counter on each creature you control
4. The Spirit token becomes a 4/4 Spirit Angel due to having a +1/+1 counter on it
5. Activate Phyrexian Altar by sacrificing the Spirit token, adding one mana of any color
6. Repeat from step 2

Results

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