Mikaeus, the Unhallowed, Altar of Dementia, and Solemnity

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Altar of Dementia on the battlefield
• Solemnity on the battlefield
• You control at least one additional nontoken, non-Human creature that does not have a +1/+1 counter on it

Steps

1. Activate Altar of Dementia by sacrificing the additional creature
2. When the creature dies, its undying ability triggers, returning it to the battlefield from your graveyard with zero +1/+1 counters due to Solemnity
3. Resolve the Altar of Dementia ability from step 1, causing target player to mill cards equal to the sacrificed creature's power
4. Repeat

Results

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