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, Soul Warden triggers, causing you to gain life.
Resolve Kor Skyfisher. When it enters, it and Soul Warden trigger.
Resolve the Kor Skyfisher trigger, returning it from the battlefield to your hand.
Resolve the Soul Warden trigger, causing you to gain life.
Repeat.
This clever loop turns the self-bouncing drawback of Kor Skyfisher into an engine by reducing its cost to a mere 2 life through the combined mana-reduction effects of Defiler of Faith and The Immortal Sun. Each time Kor Skyfisher enters the battlefield and bounces itself back to your hand, Defiler of Faith triggers to produce a 1/1 white Soldier creature token. That token's arrival triggers Soul Warden, safely offsetting the life paid to cast Kor Skyfisher while generating an endless stream of entries, exits, and lifegain triggers.