Colfenor, the Last Yew, Pawn of Ulamog, and Hangarback Walker

Prerequisites

• Colfenor, the Last Yew on the battlefield
• Pawn of Ulamog on the battlefield
• Hangarback Walker in hand

Steps

1. Cast Hangarback Walker by paying
2. Hangarback Walker enters the battlefield and dies as a state-based action due to having zero or less toughness
3. Colfenor and Pawn of Ulamog trigger
4. Resolve the Colfenor trigger, returning nothing from your graveyard to your hand
5. Resolve the Pawn of Ulamog trigger, creating a 0/1 Eldrazi Spawn creature token
6. Activate the Eldrazi Spawn by sacrificing it, adding
7. The Eldrazi Spawn dies, triggering Colfenor, returning Hangarback Walker from your graveyard to your hand
8. Repeat

Results

• Infinite +1/+1 counters on Hangarback Walker
• Infinite colorless mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers
• Infinite storm count