Cast Harald Unties the Elves by paying 2, causing it to enter the battlefield with a lore counter on it.
Harald Unites the Elves' first chapter ability triggers, causing you to mill three cards, and return Moritte from your graveyard to the battlefield as a copy of Harald Unites the Elves with one lore counter on it.
Moritte of the Frost's first chapter ability triggers, holding priority, activate Faith Healer by sacrificing Moritte of the Frost, causing you to gain 4 life.
Resolve the Moritte of the Frost trigger, causing you to mill three cards, and return Moritte from your graveyard to the battlefield as a copy of Harald Unites the Elves with one lore counter on it.
Repeat from step 3.
This clever loop centers around the unique interaction between Harald Unites the Elves and Moritte of the Frost, allowing you to continually recur a Saga that keeps entering the battlefield afresh. Because Moritte enters as a copy of the Saga—benefiting from changeling to also count as an Elf when necessary—its first chapter ability instantly triggers upon arrival, letting you mill cards and pull Moritte right back out of the graveyard. Meanwhile, Faith Healer acts as your sacrifice outlet, converting the looping enchantment into a steady stream of life by capitalizing on its mana value of 4 before the state-based mechanics of Saga completion can force it out.