Cast Whitemane Lion 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 Whitemane Lion. When it enters, it and Prosperous Innkeeper trigger.
Resolve the Whitemane Lion trigger, returning it from the battlefield to your hand.
Resolve the Prosperous Innkeeper trigger, causing you to gain life.
Repeat.
This clever self-sustaining loop relies on a clever convergence of cost-reducers to cast Whitemane Lion entirely for free. Between Oketra's Monument shaving off generic mana and Defiler of Faith discounting the remaining white mana in exchange for a bit of life, your feline rescue crew can be recast endlessly. Each iteration floods the board with tokens thanks to the tandem triggers of Defiler of Faith and Oketra's Monument, which in turn continuously buffer your life total through Prosperous Innkeeper's watchful presence.