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, Haliya triggers, causing you to gain life.
Resolve Kor Skyfisher. When it enters, it and Haliya trigger.
Resolve the Kor Skyfisher trigger, returning it from the battlefield to your hand.
Resolve the Haliya trigger, causing you to gain life.
Repeat.
This clever loop spins up infinitely by combining cost reducers with a self-bouncing creature and a life-gain payoff. With The Immortal Sun shaving {1} off your generic costs and Defiler of Faith slashing the remaining {W} in exchange for 2 life, you can cast Kor Skyfisher for absolutely zero mana. Every time Kor Skyfisher enters the battlefield, it bounces itself right back to your hand, while Defiler of Faith responds to the cast by spitting out a 1/1 Soldier token. Meanwhile, Haliya, Guided by Light sits on the board to watch the procession, turning every single creature entry into a steady stream of life.