Dark One's Dagger

The Dark One's Dagger is a magical item featured on ABC's Once Upon a Time. It first appears in the eighth episode of the first season.

Before the First Curse
The Dark One's Dagger has a curse that grants innate arcane knowledge and immense magical power to whoever's name is inscribed on its blade; this person is known as the "Dark One." Unfortunately, a person who possesses the dagger can control the Dark One and his powers. At some point of time, the Duke gained possession of the dagger when it had Zoso's name inscribed on it, and he was able to control the Dark One for his bidding. He kept the dagger hidden in his home.

The dagger was created from the tip of Excalibur, by the first Dark One, Nimue.

The curse passes from one Dark One to the next when someone uses the dagger to kill the person whose name is on the blade. Zoso, tiring of the many evil acts he was forced to commit and not wanting to be the Dark One anymore, tricks Rumplestiltskin into stealing the dagger from the Duke's home and using it to kill Zoso. When Zoso dies and Rumplestiltskin gains the powers of the Dark One, his name replaces Zoso's on the blade.

When Baelfire expresses concern for the way that the curse has changed his father, Rumplestiltskin pulls out the dagger, now bearing his name, and explains to his son that the only way to get rid of the curse is for someone to kill him with the dagger. Rumplestiltskin uses extreme caution in protecting the dagger lest he become enslaved to a master the way Zoso had or lest someone steal it and kill him so they can take his powers.

During the First Curse
When the dark curse hits the Enchanted Forest, Rumplestiltskin brings the dagger with him into Storybrooke. Although the dagger loses its magic, it still has his name inscribed on it. As Mr. Gold, he keeps it in his possession in his store until Emma Swan comes to town. Then, he takes it out into his land in the forest and hides it in the ground for safekeeping.

August Booth tricks Mr. Gold into revealing the location of the dagger and digging it up. Believing August is Baelfire, Gold hands him the dagger. Once he's in possession of the dagger, August tries to use it to control Mr. Gold, to make him use his magic to save him. Mr. Gold realizes August is not Baelfire, because his son would never use the dagger against him, and because his son knew that the dagger would have no effect in a land without magic. Mr. Gold holds the dagger to August's throat, but decides not to kill him.

After the First Curse
Mr. Gold uses it as a medium to use his Dark One's magic on the medallion and summon the wraith to go after Regina Mills to suck out her soul, giving her a fate worse than death.

While Mr. Gold is out of town searching for his son in New York City, Regina, Cora and Hook formulate a plan to find the dagger. Cora knows if they possess the dagger, Mr. Gold can be controlled to do whatever the person wants. Regina goes to the hospital and searches through an amnesiac Belle's bag to find a piece of paper with a number for a book in the library. They search through the shelves, but the book in question is missing from its place. Instead, a parchment with scribbles is found in the spot of the book. Hook believes it is a map leading to the dagger's hiding place. Cora takes the map for herself and Regina, and knocks Hook out. Once the dagger is in her possession, she plans to use it to force Mr. Gold to kill Mary Margaret, David and Emma so that Regina can finally have Henry to herself. Also, this will make Regina look blameless in Henry's eyes because she did not murder anyone.

Regina and Cora follow the map to a location in the forest behind Johanna's house, and the two wonder if the map is a trick by Mr. Gold. After overhearing their conversation, Mary Margaret goes to Mother Superior and the two try to track it down with magic. Mary Margaret suggests they make an exception and use dark magic. Emma calls from New York and Mr. Gold tells them the location of the dagger. They travel to the library attic and find the dagger hidden on the minute hand of the tower clock. Regina and Cora appear and ask for the dagger. They summon Johanna, and when Mary Margaret refuses to hand over the dagger, Regina rips out her heart. Regina begins to squeeze the heart to dust, but Mary Margaret cannot bear to watch Johanna die and drops the dagger to them. Johanna rushes into Mary Margaret's arm, but Cora sends Johanna crashing out the clock window; killing her. She and Regina disappear after their job is done. They regroup in Regina's office. Cora sits with the dagger on Regina's desk as the two talk.

While venturing the island of Neverland in search of Henry, who has been captured by Pan and the Lost Boys, Mr. Gold lights a bonfire and pulls out the dagger; standing in position so his shadow bounces onto a large boulder. Then, he slices away at the area surrounding both feet; allowing his shadow to move freely on its own. Handing over the dagger, Mr. Gold orders the item to be hidden in a place not even he himself will know where to find, which the shadowy figure swiftly follows through with.

During the Second Curse
When the Wicked Witch of the West, Zelena, had Rumplestiltskin as her prisoner, she also had the Dark One's Dagger with her to keep him at bay. Zelena also used the dagger to shave Mr. Gold and secretly obtain his blood so that she can get the Nightroot and spike David Nolan's tea with it. During this time, it's shown that true love cannot help a Dark One resist the power of the dagger; Belle tried reaching out to Gold twice, but failed.

After the Second Curse
Regina took possession of it after stopping Zelena, giving it to Belle to "curb any homicidal impulses" in Mr. Gold. However, through slight of hand inherited from his father, Gold takes the dagger and gives Belle a fake. He stabs Zelena, reducing her to dust; however, her lifeforce endured.

He later uses it as a medium to unlock the Sorcerer's hat (since Anna's tear had fallen on it, and only one who hadn't given into their darkness can open the box the hat's in). When Mr. Gold attempts the ceremony to free himself of the Dagger, Belle takes possession of it and forces him to enter the Land Without Magic; the Snow Queen's lingering magic prevented anyone who left from returning without her magic scroll. Belle then hid the dagger behind one of the hands on the face of the clock tower, keeping its location a secret from anyone else.

As result, upon his return to Storybrooke, Mr. Gold hides in the shadows to avoid being under the dagger's control. Hook even suggested he would have taken the burden of being the new Dark One if it meant putting an end to Gold's schemes; it would be a price worth paying, since he wouldn't mind having the curse broken. Taking the form of Hook, Gold convinces Belle to let him hide the dagger since her ideas for a hiding place would already be known. Gold later uses the dagger to revert Pinocchio to August to gain information on the Author of Once Upon a Time.

In the finale of Season 4, Rumplestiltskin is turned into a counterpart called the Light One when the Author writes Heroes and Villains. However, once the magic is undone, he nearly dies. However, the Apprentice sucks the darkness inside him into the Sorcerer's hat, leaving Mr. Golds heart pure white. Unfortunately, it's later revealed that this darkness was tethered to a human soul and thus began the Dark One line, to keep the evil force from destroying the realms. The only one capable of destroying the Darkness for good is the wizard Merlin. In the meantime, Emma allows herself to become the host of the darkness and thus becomes the new Dark One.

Before The Third Curse
While In Camelot, Emma gives the dagger to Regina, telling her to use it if it is necessary. After Arthur and Zelena place a spell on the other piece of Excalibur they use it to control Merlin. Arthur uses Merlin to give Emma an ultimatum: either hand over the danger, or her family and friends will be killed. When Emma meets them in the forest, they send Merlin to fight Emma. Emma, using the dagger's powers manages to fight Merlin off. She then convinces Merlin that he is stronger than the power of the sword, allowing him to become immune to it's effects. Realizing that the sword is no longer useful for control, Arthur and Zelena flee, leaving Excalibur behind. Emma then takes both the dagger and the sword to Granny's. There Merlin shows her how to reunite the dagger to the sword. After the dagger becomes a whole sword again, a previously healed injury that Hook had opens again, nearly killing him. Emma, realizing that the only way to save Hook is to tether him to the sword. Merlin and the others advise her against it, as it would be her final step into complete darkness. Not listening to their pleas, Emma takesHook to a field, and using some of her dark magic, transfers the darkness that was in Merlin into Hook. Hook disappears, leaving Emma in the field as she passes the threshold, becoming fully dark. The names on the sword change, replacing Merlin's name with Hook's. Hook is then seen rising from the Dark One's vault.

During the Third Curse
After everyone returns from Camelot, Emma keeps the dagger close to her so no one can control her. After getting Rumpelstiltskin to pull Excalibur from the stone, she forges the dagger back with the rest of the sword. When forged, the dagger loses its power making it unable to control the Dark One. However, it still bears the names of both of the current Dark Ones.

Trivia

 * The importance of the knowing name on the dagger is a play on the original Rumpelstiltskin fairytale, when he made a deal with the miller's daughter to discover his name.
 * It's existence marks a great importance to Hook as the only mentioned method of killing Rumplestiltskin, whom Hook desperately seeks to kill to avenge Milah. It is quite possibly the weapon he heard rumors of when "liberating" Belle.
 * Cora refers to the dagger as a "Kris Dagger". A kris is a prized Indonesian weapon known for its distinctive, wavy blade. They are considered to be spiritual objects.
 * If the Dark One is killed without the use of the dagger, he or she will expel the powers of the Dark One into the air after death without anyone else being next in line as the next Dark One, therefore ending the curse, however, if they are killed without the use of the dagger, they can be resurrected.
 * Belle is wearing a dagger-printed scarf.
 * The design is based on ritualistic Indonesian knives.
 * Throughout the series, the written letters of the Dark One's name keeps switching from one side of the blade to the other. Sometimes, the letters are right side up when the dagger is held in the right hand and facing the wielder with the first letter at the tip of the blade. At other times, the writing is right side up when the dagger is facing the wielder and held in the left hand with the first letter next to the hilt
 * It is currently unknown how the dagger was separated from Excalibur after being joined in Camelot.