Cast Kor Skyfisher by paying 0 and 2 life due to Defiler of Faith and The Immortal Sun.
Defiler of Faith triggers, creating a 1/1 Soldier creature token.
When the Soldier enters, Impassioned Orator triggers, causing you to gain life.
Resolve Kor Skyfisher. When it enters, it and Impassioned Orator trigger.
Resolve the Kor Skyfisher trigger, returning it from the battlefield to your hand.
Resolve the Impassioned Orator trigger, causing you to gain life.
Repeat.
This elegant loop transforms the humble Kor Skyfisher into a self-sustaining engine by removing its mana cost entirely. With The Immortal Sun and Defiler of Faith both reducing its cost by a combined {1}{W}, the white permanent can be cast for free while you pay 2 life instead, which simultaneously triggers the Defiler to produce a 1/1 Soldier creature token. Every time a creature enters the battlefield—including that Soldier token and Kor Skyfisher itself—Impassioned Orator rewards your persistence by gaining you life. Finally, Kor Skyfisher's own entry trigger forces it to return a permanent you control to your hand, naturally picking itself back up so you can repeat the entire process indefinitely.