Pandora's Box is a magical box-like artifact and an item featured in the Once Upon a Time series.
In Storybrooke, Pandora's Box is one of the numerous items Mr. Gold keeps locked up in his pawnshop. Previously, he enchanted the box's hiding spot that can only be triggered if and when the chipped cup is placed back into its saucer in the cupboard. After Mr. Gold goes to Neverland save Henry, he believes must die in order to defeat Peter Pan and decides to sacrifice himself, but many complications arise. Eventually, he and Regina form a plan to retrieve a box, which has enough evil stored inside it that Mr. Gold believes will be enough to defeat Pan. Regina strikes a deal with a mermaid, Ariel, to bring it back, but he can't tell her what the item is without Pan possibly finding out as well. Mr. Gold sends her off with a magically enchanted sand dollar to give to Belle. Upon reaching the shores of Storybrooke, Ariel does not realize she is secretly being watched by two of Pan's accomplices, John and Michael Darling, who make it their sole mission to stop her from sending the box back to Mr. Gold.
When Belle receives the sand dollar from Ariel, she uses it to trigger a clue from Mr. Gold about the item's whereabouts, which can be found "with the strength of their love". She decodes the message, realizing that Mr. Gold is referring to the chipped cup, which symbolizes how much wear and tear their love has endured. By placing the cup back in its saucer, she activates a hidden compartment in the floor, and opens it to pick up Pandora's Box. As Belle read in a book, legend states the box contains the world's darkest evil. They are ambushed by John and Michael, who then tie the two women up and take the box to destroy it in the mines using a dwarf ax. Ariel and Belle make it just in time to stop them. John and Michael are knocked off their feet after Belle sets a mine cart in their direction, and snatches the box back. They begin pleading for Belle not to help Mr. Gold, and eventually reveal they are helping Pan only because he has their sister Wendy captive in Neverland. Belle promises them the box is the key to destroying Pan for good so Wendy can be free, to which they agree with the plan. Ariel swims back to Neverland and delivers the box to Mr. Gold, but requests as gratitude that he save Wendy.
Per chance, Mr. Gold and Regina regroup with David, Emma, Hook, Mary Margaret, Neal and Tinker Bell and give news about the box's power to contain Pan. Still distrustful of Mr. Gold, Neal asks for him to fork over the box. His father concedes with the demand, and the box remains in Neal's hands until the two of them as well as Emma and Regina breach the cave entrance of Skull Rock, where Henry and Pan are currently stationed, and discover a barrier keeping out anyone who has a shadow. Since Mr. Gold is the only one without a shadow, the box is reclaimed by him and he alone ascends up to the upper level to confront Pan. When the two come face to face, Pan attempts a heartfelt father-to-son conversation with Mr. Gold to affirm he does indeed care for him. He asks Mr. Gold to choose him instead so they can start over, but this is met with refusal. Mr. Gold motions to use Pandora's Box, but then Pan pulls out an identical replica. As it turns out, Pan is in possession of the real one while the other is a fake. At once, he opens the box and successfully contains Mr. Gold within it.
Pan succeeds in gaining Henry's heart and becomes immortal. He leaves for his special hiding place, known as the "thinking tree", in Pixie Woods. Suspecting Henry's family will retaliate against him, he plants the box out in open view near the tree. Emma, Mary Margaret and Regina arrive shortly after looking for Pan and fall victim to being ensnared by the tree's thick vines. Pan acknowledges the tree is where he abandoned his own son, Mr. Gold, shocking them with this piece of information. Nonetheless, he is quite relieved his son is no longer a burden since being locked up in the box. Pan's next move is destroy all three women with the thinking tree, which attacks anyone feeling regret, by bringing up each of their pasts that will cause the emotion to arise. Only Regina regrets nothing, and frees herself and her allies from the vines, to tear out Henry's heart from his chest and also steal the box back. They leave to board the Jolly Roger for the journey home, but first, the heart is returned to Henry's body, thus reviving him from death. Neal lets Mr. Gold out from the box and the two reconcile. Mr. Gold admits he didn't tell Neal that Pan is his father out of fears of making the same mistakes as his own parent. Neal corrects him, and states Mr. Gold is not at all like Pan. Then, Mr. Gold himself traps Pan in the box when he catches him attempting to rip away Henry's shadow. He remains unaware that, at the last moment, Pan switched bodies with the boy, saving himself while Henry, now stuck in a different body, is sucked into the box.
After a safe arrival to Storybrooke, Mr. Gold seals the box in his pawnshop to prevent Pan from ever escaping. However, little does anyone know that Pan begins carries out his plan of wreaking havoc by freeing the Shadow, who then kills Mother Superior. This leads the townspeople to believe Pan is controlling the Shadow from inside the box. While in Henry's body, he is taken by Regina to her vault for protection against Pan. Meanwhile, Emma and her parents track down Mr. Gold so he can give them box. Emma steps past the town border as Mr. Gold releases Pan from on the same side as her to render him powerless. Puzzled, Henry finds himself in Pan's body as Emma points a gun in his direction. He claims to be Henry, so Emma tells him to name the first time they ever connected together. Henry correctly recalls this took place at the castle playground when he realized Emma gave him up at birth to better his chances in life. having received proof, Emma believes him and they reconcile with a hug. They hurry to the vault to tell Regina about the body switch.
- It is named after the well-known accursed object in Greek mythology which first appeared in Hesiod's Works and Days as a pithos (a jar) that contained all the evils in the world.
- The Greek text carved into the lid of Pandora's Box says "ΛΕΙΤΟΥΡΓΕΙ ΜΕ", which translates as "open me". The Greek letters Alpha and Omega (Α and Ω) are carved into the side of the box.