Luminous Broodmoth + Felidar Guardian + Gravity Sphere + Phyrexian Altar

Luminous Broodmoth

Felidar Guardian

Gravity Sphere

Phyrexian Altar

How it works

1. Sacrifice Felidar Guardian to Phyrexian Altar to add 1 mana of any color.
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.