Cast Phlage either from your hand or from the command zone by paying 1 plus commander tax, if applicable.
When Phlage enters the battlefield, its first and second abilities trigger.
Resolve the second trigger, dealing 3 damage to any target and causing you to gain 3 life.
Resolve the first trigger, causing you to sacrifice Phlage.
When Phlage dies, Luminous Broodmoth triggers, returning Phlage from your graveyard to the battlefield without a flying counter on it due to Solemnity.