[s4e23] Operation Mongoose (2) -

: The freed darkness attempts to possess Regina. To protect her friend’s hard-earned happy ending, Emma Swan sacrifices herself by tethering her soul to the darkness. She vanishes, leaving behind the Dark One's dagger, which now bears her name.

is the 23rd episode and second half of the two-hour Season 4 finale of Once Upon a Time , which originally aired on May 10, 2015. The episode concludes the "Heroes and Villains" arc, following Henry’s quest to restore reality after the Author, Isaac Heller, rewrote the lives of the residents of Storybrooke into a "Bizarro" Enchanted Forest where villains win and heroes lose. Plot Summary [S4E23] Operation Mongoose (2)

Upon returning to Storybrooke, the characters face immediate new threats: : The freed darkness attempts to possess Regina

: In the rewritten world, familiar characters have swapped roles: Snow White is a cruel Evil Queen, Regina is a powerless bandit, and Rumplestiltskin is a valiant "Light One" knight. Emma is imprisoned in a tower without magic, while Hook is a cowardly deckhand. is the 23rd episode and second half of

: Gold is dying because his heart has turned completely black from his dark deeds. The Apprentice attempts to draw the darkness out and trap it in the Sorcerer's Hat, but the darkness is too powerful to be contained.

: Before dying from the darkness's attack, the Apprentice reveals that only the Sorcerer, Merlin , has the power to destroy the darkness forever, setting the stage for Season 5. Key Revelations & Details Once Upon a Time season 4 finale recap: Operation Mongoose