Scarecrone, Thornbite Staff, Cathodion, and Phyrexian Altar

Prerequisites

• Scarecrone on the battlefield
• Thornbite Staff on the battlefield
• Cathodion on the battlefield
• Phyrexian Altar on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing Cathodion, adding
2. Cathodion dies, triggering itself and Scarecrone
3. Resolve the Cathodion trigger, adding
4. Resolve the Scarecrone trigger, untapping it
5. Activate Scarecrone's second ability by paying and tapping it, returning Cathodion from your graveyard to the battlefield
6. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers