Blightbeetle, Altar of Dementia, and Harmless Offering

Prerequisites

• Blightbeetle on the battlefield
• Altar of Dementia on the battlefield
• Harmless Offering in hand
• available

Steps

1. Donate Blightbeetle to an opponent Activate Altar of Dementia by sacrificing the undying creature
2. When the undying creature dies, its undying ability triggers, returning itself from your graveyard to the battlefield without a +1/+1 counter on it due to Blightbeetle
3. Resolve the Altar of Dementia ability
4. Repeat from step 2

Results

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