Phyrexian Altar, Hardened Academic, and Obstinate Gargoyle

Prerequisites

• Phyrexian Altar on the battlefield
• Hardened Academic on the battlefield
• Obstinate Gargoyle on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing Obstinate Gargoyle
2. When Obstinate Gargoyle 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 Obstinate Gargoyle
4. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite colored mana
• Infinite death triggers
• Infinite sacrifice triggers