Traveling Plague, Altar of Dementia, and Siona, Captain of the Pyleas

Prerequisites

• Traveling Plague in hand
• Altar of Dementia on the battlefield
• Siona, Captain of the Pyleas on the battlefield
• available

Steps

1. Cast Traveling Plague by paying , attaching it to another creature you control
2. When Traveling Plague enters, Siona triggers, creating a creature token
3. Activate Altar of Dementia by sacrificing the creature Traveling Plague is attached to
4. When the creature dies, Traveling Plague triggers, returning itself from your graveyard to the battlefield attached to the token created in step 2
5. When Traveling Plague enters, Siona triggers, creating a creature token
6. Resolve the Altar of Dementia ability
7. Repeat from step 3

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill