Luminous Broodmoth + Felidar Guardian + Gravity Sphere + Altar of Dementia

Luminous Broodmoth

Felidar Guardian

Gravity Sphere

Altar of Dementia

How it works

1. Sacrifice Felidar Guardian to Altar of Dementia to mill target player for 1.
2. Luminous Broodmoth triggers, returning Felidar Guardian to the battlefield with a flying counter on it.
3. Felidar Guardian's ETB triggers, exiling Mystic Decree and then returning it to the battlefield.
4. Repeat.