Cast Kor Skyfisher by paying 0 and 2 life due to Defiler of Faith and Oketra's Monument.
Defiler of Faith and Oketra's Monument trigger.
Resolve the Defiler of Faith trigger, creating a 1/1 Soldier creature token.
When the Soldier enters, Prosperous Innkeeper triggers, causing you to gain life.
Resolve the Oketra's Monument trigger, creating a 1/1 Warrior creature token.
When the Warrior enters, Prosperous Innkeeper triggers, causing you to gain life.
Resolve Kor Skyfisher. When it enters, it and Prosperous Innkeeper trigger.
Resolve the Kor Skyfisher trigger, returning it from the battlefield to your hand.
Resolve the Prosperous Innkeeper trigger, causing you to gain life.
Repeat.
This charming loop transforms Kor Skyfisher into a self-returning engine by leveraging multiple cost-reducers—namely Defiler of Faith and Oketra's Monument—to slash its mana cost all the way down to zero. As you repeatedly cast the Kor Skyfisher for free by paying 2 life, both Defiler of Faith and Oketra's Monument trigger to flood the board with Soldier and Warrior creature tokens. Every time one of these tokens or the Kor Skyfisher itself enters the battlefield, Prosperous Innkeeper notices and keeps your life total safely padded while simultaneously generating Treasure tokens from its own entry, giving you an endless procession of enters-the-battlefield triggers.