Not all wizards have long, white beards.
Merlin is a supporting character on Once Upon a Time. A normal man whose life forever changed when he drank from the Holy Grail and received powerful magic, along with immortality and the ability to see the future. The Sorcerer is what he became known as, and he fell in love with a woman named Nimue, who also ended up drinking from the Grail and receiving her own magical powers... but she used hers to kill, and so they turned dark, and she later trapped her fiancée as a tree for millennia. When he was finally freed, he was tasked with helping Emma Swan turn away from the darkness, but ended up a victim of it when his powers were harvested and a new, more ruthless Dark One ripped his heart out and crushed it to service a curse.
Before the Curse
I have magic...
Merlin is blessed with magical powers. ("Nimue")
1000 years before the Age of Arthur, Merlin and his companion, Adda, are escaped soldiers running through desert wastelands when they begin to collapse due to exhaustion and thirst; that is, until Merlin notices what Adda thinks is a mirage and heads toward it. As it turns out, it's the holy grail. While Adda turns to dust upon touching it, Merlin drinks from it and receives new magical powers, as well as the ability to see the future and immortality. 500 years later and Merlin has transformed the desert into a place of considerable beauty, having gained an Apprentice as well as a position as the village healer. One day, a woman named Nimue whose future he cannot see asks him for a favor; her village was burned down by a man named Vortigan, and all she managed to escape with was a handful of middlemist seeds. Her greatest revenge would be for them to prosper in spite of him, and so Merlin uses his magic to create a healthy growth of them, then entering a relationship with Nimue. He wants to propose but is fearful because he is immortal and she isn't, and so the two of them quest to the Flame of Prometheus so that Merlin can remold the holy grail into a sword that is capable of cutting away his magic. When he does so, however, Vortigan arrives and attacks Nimue, causing her to bleed out in Merlin's arms. Vortigan then takes the sword and tries attacking Merlin with it, only for Nimue to rip his heart out. She explains that she earlier drank from the grail and gained her own magic, and proceeds to use it for proper revenge by crushing Vortigan's heart and killing him. This turns her magic dark, and thus she becomes the first Dark One. She takes the sword and breaks it against the Promethean flame's stand, with the flame itself having gone out, to avoid her magic and immortality being cut away. Merlin hides the sword - Excalibur - in a stone while fashioning its tip into a dagger and binding it to Nimue's soul so that she may remain under control. She, meanwhile, adopts Vortigan's mask and begins a reign of terror. ("Nimue")
Merlin sheds tears for his lost love, which leads to him becoming a tree. ("Dreamcatcher")
Merlin is wandering through the nighttime forests of Camelot with the Dark One's dagger in tow, while the Dark One herself travels in swift, fleeting movements all around the powerful Sorcerer. Using the dagger, the latter is able to command the evil magical being - his former true love - to stop, and she stands to face him - a cloaked figure swathed all in black save for the golden mask that adorns her face. She stands there, staring at him, and Merlin is in tears; he tells the darkness that it destroyed the only woman he ever loved... and so now he shall destroy it. He raises the dagger, ready to kill the Dark One, but he hesitates. She continues to stare at him while he continues to weep. Finally, he utters that he can't do it, proceeding to drop to the floor. The Dark One sees that her dagger has been dropped also and promptly picks it up, then holding Merlin's head up by the hood as he professes that he misses his lost love and collecting one of his heartbroken tears with the blade. It glows purple for a moment, and the Dark One is then able to wield this power to turn Merlin into a tree. He stays in this state for a long passage of time. ("Dreamcatcher")
Merlin shelters young Arthur and Guinevere. ("The Broken Kingdom")
A young peasant boy by the name of Arthur claims to his friend Guinevere that the great Sorcerer Merlin is trapped within a large, magical tree in their village, and that said tree told him a prophecy that, one day, he would be the one to relieve Excalibur from the stone, therefore becoming King of the broken kingdom of Camelot. He is bullied for these predictions, but ultimately Merlin's prophecy comes to pass, and Arthur is crowned. However, to his horror, when he does finally draw Excalibur, its tip is missing - its other half is the Dark One's dagger, and Arthur works tirelessly to find it, all the while lying to his people and becoming so strung-out that Guinevere is almost driven into the arms of another man. The King continues to transcribe Merlin's prophecies, giving him answers such as how to enter the Vault of the Dark One, but all he's able to obtain is some magic sand that makes his broken kingdom - and marriage - appear fixed. ("The Broken Kingdom")
Merlin learns of the Author's misdeeds. ("Lily")
The Apprentice rushes into the Sorcerer's lair in order to warn him of the fact that the Author forsook his holy duty by using his magic to manipulate events majorly, having made it so that Maleficent's child had the savior's darkness siphoned off into her before being banished to a land without magic. The Apprentice warns the Sorcerer not to worry, however, for he trapped the Author inside the book - from inside it, he may only be able to record events; manipulation is impossible. He is curious as to what will become of Snow's and Maleficent's respective daughters, and the disembodied Sorcerer says that their fates shall remain entwined, just as they always were, telling his Apprentice to just make sure that the Author is never allowed to manipulate fate ever again. ("Lily")
After the Curse
One day, you'll have the opportunity to remove Excalibur from its stone, and you mustn't. Leave the sword alone.
Merlin gives Emma an important warning. ("The Dark Swan")
A six-year-old Emma Swan heads into a movie theater in Minneapolis to view a screening of The Sword in the Stone, however, because she can't afford her own snacks, she ends up stealing an Apollo bar from some woman's coat pocket. When she takes a seat and begins to unwrap it, Merlin, disguised as an usher, tells her, "Don't." She wonders what he means and he repeats himself, going on to say that, one day, she's going to have the opportunity to pull Excalibur from the stone, just like the young man Arthur is doing in the movie. However, she shouldn't, because if she does then bad things are sure to happen. She heads this warning before Merlin is shushed by some little girl in front of them, and then he disappears suddenly, leaving Emma mightily confused as she watches the cartoon boy pull the sword free. ("The Dark Swan"/"The Bear and the Bow"/"Nimue")
Before the Third Curse
Darkness like this takes a hold of a person, find its way deep inside, where nobody else can see. So if I am to free you from its grasp, I must know one thing. Emma, is your heart truly ready to be free? Because it is as much up to you as me.
The heroes are surprised to find Merlin trapped in a tree. ("The Price")
When Emma and the others are welcomed into Camelot by King Arthur and the Knights of the Round Table, they are told that, due to the fact that Merlin prophesied their arrival, enough time was had to organize a royal ball in their honor, which they all look forward to. They proceed to wonder when the quest to find Merlin will begin, but Arthur reveals that no questing will be involved - he already knows exactly where Merlin is. It is then that Emma, Regina, Robin, David, Mary Margaret and Hook are taken outside and told of Merlin's fate. The latter is shocked that the most powerful sorcerer in all the realms is trapped inside a tree, and Arthur assures the pirate that he expressed the same exact sentiment the first time he saw it too, but all hope is not lost, for Merlin also prophesied that one of them is the savior who will be able to free him. This regards Emma, but Regina pretends to be the savior so that Emma, being the new Dark One, won't be forced to give in to her dark impulses by using dark magic. Regina and Robin later peruse the tree when Sir Percival approaches the former to give her a necklace, which turns out to be enchanted to spy on her. He learns that she's really the Evil Queen and makes an attempt on her life, only to end up dead himself. ("The Price")
Merlin is freed. ("Dreamcatcher")
Emma enchants a dreamcatcher in order to see how Merlin became a tree, learning that the Dark One used the Sorcerer's tear, which was shed due to heartbreak. As such, Regina deduces that a similarly-shed tear will be the key ingredient in freeing him, and so the dreamcatcher is used to make her relive the loss of her first love Daniel. However, since her heartbreak isn't fresh enough, with her having moved on with Robin Hood, the spell doesn't work, and they have to use Henry's tears instead when his first crush Violet tells him that she's only interested in being his friend (in fact, Emma manipulated the situation by ripping out the girl's heart and forcing her to say these things). Arthur and his knights charge at them as they're about to do the spell, to little effect, and it isn't long before Emma drops in the tears and wields masses of both light and dark magic. She converges it on the tree and, finally, Merlin is freed. He greets Emma, having been expecting her, while he cites Arthur as a disappointment, to his anger. The Sorcerer is then taken to Granny's Diner where he unfreezes Emma's parents, using his magic to take off the enchantment that Arthur had Guinevere put on them. They wonder if he's able to remove the darkness from Emma, and he says he can... provided Emma's heart is ready to let it go, which she seems unsure of. ("Dreamcatcher")
Merlin reiterates his warning. ("The Bear and the Bow")
The door to Arthur's dungeon in Camelot bursts open, and Charming and Hook come on through, easily besting the guards on the other side who have already been weakened by Merlin's magic. The Sorcerer himself is there too, followed by Belle, and easily knocks out more guards on the way, commenting that wielding magic is just like riding a bike. Charming wonders how he knows what a bike is, and Merlin asks the prince if he thought all of his prophecies came true due to luck, then beckoning each of his new allies to hide while a group of guards goes past. Hook realizes that the Sorcerer really can see the future, and the small group go on to find Lancelot's cell. At first, the former Knight of the Round Table is worried by the prince, but he assures him that he and Snow are now free of Arthur's control. Lancelot wonders how they got free, at which Merlin reveals himself; Lancelot is humbled, and Merlin proceeds to have trouble getting the bars off his cell - as well as Merida's, which is opposite. Belle shows him a passage from her book that she believes might be helpful, and it is; the Sorcerer cites her as clever before successfully freeing the prisoners. Later, Charming and Lancelot can be seen in Granny's Diner while Merlin reminds Emma that they once met when she was a child. He warns her once again not to pull Excalibur from its stone when the time comes. ("The Bear and the Bow")
Merlin is tethered to Arthur's broken sword. ("Nimue")
Merlin explains that he and Emma will be questing to the Flame of Prometheus to receive a spark capable of reforging both halves of Excalibur, but in order to complete the process he needs for the others to find a way to steal Arthur's broken sword. He tells Emma that in order to gain the spark, she's going to have to pull the ember from the first Dark One, who shall appear to her through vision and give her the toughest test yet in terms of battling the darkness. They soon make it to Oxleigh and beyond where the Promethean flame used to burn, and Emma holds up the Dark One's dagger - which Merlin took without permission - and uses it to summon the first Dark One. To her shock, it isn't a man like she expected, but rather Merlin's first true love Nimue. She tries convincing Emma to kill Merlin, forcing her to strangle the Sorcerer with a single hand, yelling in her ear the entire time. She encourages Emma not to go back to being nothing, at which the darkened savior exclaims that she is not nothing and was never nothing and that the power the darkness offers is unneeded by her. She backs off of Merlin and forces the ember from Nimue, who assures her that she's not dead yet and shall remain in her head before disappearing. Merlin, meanwhile, gets to his feet and asks Emma how it felt to take the hard path; she says that, to be honest, it felt damn good. The two of them begin trekking back and Merlin explains how he hid the sword away in the stone and forged the dagger from its broken end to keep Nimue under control after she turned... but then she got it away from him and turned him to a tree. Emma wonders if there could ever be a Dark One to use their powers for good, but Merlin tells her not to let such thoughts tempt her, pointing out that if they are successful in destroying the darkness then they won't have to ask that much of anyone. The Sorcerer is suddenly pulled away by Arthur, whose end of the sword has been tethered to Merlin by Zelena. He controls him now, and orders him to make the heroes disappear from the throne room after they've broken in. ("Nimue")
Merlin's magic is extrapolated. ("Birth")
Having bound the heroes to trees, Merlin approaches Emma to tell her that if she ever wants to see her loved ones again then she is to hand over the dagger and the Promethean spark to Arthur and Zelena, the former of which now controls him. Emma arrives to pay the ransom, but when Zelena opens the box containing the spark, a magical booby-trap attacks her and ties her to a tree. In retaliation, Arthur orders Merlin to kill Mary Margaret, and so Emma pep talks him into resisting by reminding him that he's the most powerful good wizard who ever lived and if he can't resist the darkness then no one can. He manages to temporarily relinquish, giving Hook enough time to wriggle free and wrestle Excalibur from Arthur, receiving a cut to the neck in the process that Emma soon heals. When Emma is ready to light the spark finally, Hook collapses because his wound reopens, and Merlin explains that a cut given by Excalibur is never meant to heal, and Hook starts to die. Refusing to accept this, Emma teleports herself and her boyfriend to a field of middlemist flowers where she uses the broken Excalibur, as well as the Promethean spark, to extract Merlin's powers from him, transferring them into Hook. This causes the powers to turn dark and for Hook to become a new Dark One, proceeding to rise from the associative vault. ("Birth")
Merlin is murdered by one Dark One, and mourned by another. ("Broken Heart")
Merlin and the others head to the Vault of the Dark One where the former Sorcerer assures that it most definitely has forged Hook as its newest Dark One, meaning that Emma went through with what she planned and must have turned fully dark in the process. Lancelot is sent to ask his mother, the Lady of the Lake, for help, for they're going to need all the allies they can get if they're going to be facing two Dark Ones, the both of which soon return to Granny's Diner after everyone else has made it back there. Merlin is in the middle of recording a warning for the others, telling them that their only hope lies with Nimue, when Hook enters the diner and confronts him alone, explaining to him that Nimue still lives on inside of him, meaning that if he were to cast a new Dark Curse, then her love for Merlin would allow for his heart to work as sacrifice. As such, the new Dark One rips out the former Sorcerer's heart and crushes it to dust over his cauldron, enacting a new curse that should return everyone to Storybrooke so that Hook can finally kill Mr. Gold. Emma witnesses this and turns Merlin's body to dust, hoping that he may rest in peace. She then wipes everyone's minds using her dreamcatchers before the curse is complete, so as to have a blank slate when she arrives home to start working on a way to remove the darkness from both herself and Hook. ("Broken Heart")
There is only one person who can help me defeat the Dark One now: her name is Nimue.
Merlin's voicemail is received. ("The Bear and the Bow")
Regina reveals that Emma was successful in freeing Merlin in Camelot, to the surprise of the others. The question is raised of why he didn't remove the darkness from her, and Regina proposes that they find out by communicating with him, having figured out a spell that will allow them to do so using the Crimson Crown. Belle is upset that everyone seems less concerned with rescuing the captive Mr. Gold and storms out, proceeding to be chased by Merida and her arrows in the Dark Swan's attempt to make her predecessor brave. Meanwhile, a cauldron is prepared down in Regina's vault, and all that's needed to reach the Sorcerer is for one of his "chosen" to drop the Crimson Crown into it; they summon Arthur, who suggests that he do it alone since no one else has ever been around when he received Merlin's prophecies in the past. Not wanting to take any risks, they all give him his privacy... only for him to throw the magical toadstool onto the fire beneath the cauldron, clearly not wanting the heroes to contact Merlin. This is deduced when the reasonably Crimson Crown is found merely charred - for magical toadstools don't burn - and Regina realizes that there's one other person in town who was chosen by Merlin: the Author. As such, they have Henry drop the toadstool into the cauldron and the message from Merlin appears, suggesting to them that Emma did something awful to him during the missing six weeks; they are told that their best hope lies with Nimue. ("The Bear and the Bow")
Gallery of photographic stills released to promote the character.