Shilgengar, Sire of Famine, Hardened Academic, and Persistent Constrictor

Prerequisites

• Shilgengar, Sire of Famine on the battlefield
• Hardened Academic on the battlefield
• Persistent Constrictor on the battlefield

Steps

1. Activate Shilgengar by sacrificing Persistent Constrictor
2. When Persistent Constrictor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Hardened Academic triggers, putting a +1/+1 counter on Persistent Constrictor
4. Resolve the Shilgengar ability
5. Repeat

Results

• Infinite Blood tokens
• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite sacrifice triggers