Jumbo Cactuar, and Altar of Dementia

Prerequisites

• Jumbo Cactuar on the battlefield
• Altar of Dementia on the battlefield
• undefined

Steps

1. Declare Jumbo Cactuar as an attacker, triggering its ability, giving it +9999/+0 until end of turn
2. Activate Altar of Dementia by sacrificing Jumbo Cactuar, causing a player to mill their library

Results

• Infinite self-mill
• Infinite mill for target opponent