Everyone sees their worst self differently: some as a mirror image, others as a literal monster. However the mind conjures it.
Mr. Hyde is a supporting character on Once Upon a Time. Having emerged freely from the body of Jekyll, Hyde is the physical manifestation of the doctor's worst self - all the parts that he would hide away from the world, hence the name. Hyde managed to establish himself as a worthy adversary to Storybrooke and its heroes, but in the end he wasn't the monster they needed to worry about. While Hyde had the capacity to love, Jekyll still had the capacity for evil, and him dying a judicious death meant that his previously indestructible other half was doomed to suffer the exact same fate.
Before the Curse
Mary's death is pinned on Hyde. ("Strange Case")
Dr. Jekyll spends years working on a serum that should be able to separate one's good half from their evil half, and Rumplestiltskin finally helps him complete it, convincing him to drink it and try it out for himself so that he can use his evil half to convince Dr. Lydgate to finally give him that academy membership he's always wanted. When he drinks the serum, his other half is surprised to see such a change in appearance, and Rumple explains that he is all the parts Jekyll wanted to hide from the world - which suggests the perfect name: Mr. Hyde. Hyde introduces himself as such to Dr. Lydgate and his daughter, Mary, whom Jekyll has spent a long time pining for. He then threatens to reveal Lydgate's affair with his lab assistant should he not hand over an academy pin for Jekyll, and the next morning the doctor is thrilled to learn that the serum was a success. However, Rumple says that one success proves nothing, and convinces him to drink it again so as to have Hyde seduce Mary on his behalf. This backfires when Mary reveals to Hyde that she has no interest in Jekyll, and she ends up sleeping with the doctor's other half instead. When he wakes up, as Jekyll, he is enraged that she took Hyde to bed, and then he kills her in a struggle by pushing her from a window. He proceeds to pin it on Hyde by quickly downing the serum, and then a witch hunt is instigated against him all across the city. Back at the lab, he is met by Rumple, and he sees the whole experiment as a failure when he learns that Hyde had the capacity for love - for he loved Mary. He wants to kill him, but decides to punish him by condemning him to a life attached to his weaker half, and by banishing them both to the Land of Untold Stories. ("Strange Case")
After the Third Curse
Mr. Hyde comes out to play. ("Only You")
In the Land of Untold Stories, Hyde is the darker side of Dr. Jekyll. While Hyde is dormant Jekyll takes control over their body, so Hyde hires an orderly to prevent Jekyll from escaping. When Jekyll secretly picks some flowers that will serve as the final ingredient for a serum which will permanently separate himself and Hyde into two bodies, he runs into Snow, David, Hook and Zelena, who ended up lost in his world. The group end up being captured and Hyde visits them in their cell. Believing they work for the Dark One, he begins to choke Hook, but releases him when Snow convinces him Rumple is their enemy. Later, while Hyde is dormant, Jekyll visits the prisoners and agrees to help fix their broken wand if they take him home with them, however, Poole catches the doctor and forces him to ingest a serum to wake Hyde up. Hyde becomes interested in the wand's power because it can open a portal to his prisoner's realm. He uses it to steal Pandora's Box which contains Belle, and plans to use it against Rumple as leverage. ("Only You")
Hyde and Jekyll become separated. ("An Untold Story")
Hyde returns to his dormant state and Jekyll awakens in a straitjacket, preventing him from escaping. However, with Poole asleep, he manages to free himself and steal the key to rescue their prisoners. Jekyll completes the serum at Hyde's house but Poole arrives and prevents him from taking it, instead giving him a potion to awaken Hyde. Zelena attempts to blast him with magic, but he just absorbs it, unaffected. Hyde then ingests the complete serum and splits himself and Jekyll into two bodies. Deeming Jekyll disappointing and pathetic, he tries to choke him, but Hook rescues him just in time. Jekyll escapes with the group but they run into Hyde on the city streets later. Their confrontation comes to a sudden halt when pennies begin to rain from the sky and a watery portal opens up. Everyone except Hyde jumps through it, returning to the Land Without Magic. Rumple, who snuck through the portal to arrive in the Land of Untold Stories, visits Hyde to retrieve Pandora's Box. ("An Untold Story")
Hyde speaks of the Temple of Morpheus. ("The Savior")
Desperately wanting the information that Hyde allegedly possesses that will allow him to wake Belle, Rumple listens to the terms of the agreement that the evil warden wants to make, soon finding out that the latter would like to become Storybrooke's new "owner" so that he can take some of his friends from the Land of Untold Stories there and allow their unfinished stories to play out the way they were supposed to... and wreak some havoc. Not really caring about the people who refused to allow him to try and wake his true love, Rumple nonchalantly hands over the proverbial keys to the town, thereby revoking his own often forgotten ownership and making it so that the place officially belongs to Mr. Hyde. With this, Hyde provides the Dark One with a map to the Temple of Morpheus, explaining to him that, inside, there are magical sands that, when sprinkled over a sleeping person, will allow one to enter a dreamer's mind. Gold need simply pour the sand over Belle and enter her dreams, and then, from there, he should be able to pull her out of her sleeping curse. With that, Gold sets out on his quest while Hyde and his friends head on over to Storybrooke to claim it as their own. ("The Savior")
Hyde claims Storybrooke as his own. ("An Untold Story")
Shortly after Regina destroys the Olympian Crystal and releases the magic back into Storybrooke, Hyde arrives to the town and tells Regina and Henry how he'd hate to be trapped in the town without magic. Henry knows who this evil man is and he demands to know how he got there, but Regina already knows that it was Gold, presuming that he made a deal with the warden. Hyde confirms this, explaining that he provided the Dark One with some information in exchange for Storybrooke. "Excuse me?" Regina retorts, and Hyde tells her that Storybrooke is his now, and he brought some friends. He smiles, telling the mother and son that he's been looking for a place like this for quite some time: a land where all the world's lost and forgotten stories could play themselves out. And now that he's brought them there, that is exactly what they're going to do. Not liking this one bit, Regina approaches this new villain threateningly, wanting to tell him something, "Mr. Hyde." She claims to know how his story ends and reveals that he loses; however, his smile refuses to waiver as he tells her that he wouldn't bet on it, "Regina." He adds that, despite what she may think, darkness is not as easy to snuff out as she might believe. The Mayor finds this daunting, and Hyde shoots her one last cheeky look before heading off to explore the town that he now owns. Regina, meanwhile, is left to ponder the implications of what he's just said to her. ("An Untold Story")
Emma asks a detained Hyde for info on her tremors. ("The Savior")
When a dirigible carrying Hyde's "friends" from the Land of Untold Stories flies over Storybrooke, a group gather in the woods to follow it. Hyde appears, so Emma and Regina attack him. They try to blast him with their combined magic, but he is unaffected by it. He goes on to warn everyone that there's nothing more dangerous than an untold story. Later on, Regina shows up outside the mayor's office with Dr. Jekyll, pretending to hold him hostage while Emma hides nearby with a weapon that can subdue Hyde. Regina offers Jekyll to Hyde in exchange for him leaving town, but Hyde threatens to kill the former queen unless she hands him over. He begins to strangle Regina, but Emma's hand tremors prevent her from using the weapon straight away. Eventually she does and Hyde is detained. Whilst being taken away, Hyde taunts Emma over her tremors, hinting to know the source of them. Emma visits Hyde in his cell, and after a long conversation, he tells her the location of a person who can reveal what her tremors mean. After she discovers they mean she's destined to be cut down by a villain, she returns to Hyde, angry that he knew what she'd find out. Hyde warns her that the villain in her visions could be anyone, and when she suggests helping them in order to prevent her fate, he points out that this may be the very thing that leads to her death. ("The Savior")
Hyde and the Evil Queen take a little walk. ("The Other Shoe")
The Evil Queen pays Hyde a little visit in his cell, pampering him with food and decoration in exchange for information about the people he brought over from the Land of Untold Stories. This means that when Regina arrives, wanting to use her lasagna as leverage to learn from Hyde how the Evil Queen managed to survive getting her heart crushed, he is already sated, and his price of information has gone up. He points out how hard it must be for Regina to be going up against herself and, later, Hyde is paid yet another visit by the Mayor's evil other half. She wants his help, considering her plan to have Cinderella's untold story end in bloodshed was a failure, but he makes clear how hard it is to help her while chained up in a cell. As such, the Queen uses her magic to remove his shackles and opens up his cell door, then suggesting that the two of them take a walk and casually strolling out of there with him at her side. Walking arm-in-arm with the wicked monarch, Hyde is overjoyed to finally be free. ("The Other Shoe")
Jekyll's death means that Hyde dies too. ("Strange Case")
Hyde and the Evil Queen head to Gold's shop for a cameo necklace that belonged to Mary, and the enraged Dark One attempts to kill Hyde when he offers nothing in return... only to then discover that he can't be killed, which is of deep dismay to him when Hyde threatens to harm Belle. He plants the necklace in Jekyll's room and, thanks a beckoning spell put on it by the Queen, it leads the two villains right to the doctor's lab where, currently, he is attempting to replicate his serum in the hopes that it can be used to destroy the doppelgangers. Hyde trashes the lab and, knowing Jekyll will try to preserve a vial of serum on his person, manages to switch it with a fake. He then trolls the woods, where the heroes are searching for him, and manages to escape Emma and David by subverting their attacks. While running, he is stabbed by Gold's dagger, but it has no effect on him thanks it it having been doused in a fake serum, and then Hyde destroys the real serum. Now though, he has possession of the Dark One's dagger, and he uses it to force Rumple to take them both to the town docks. He reveals there to be one final twist in their story: Hyde isn't the monster Gold should be worried about. The two of them then watch while Belle, who's been confined to the Jolly Roger for her "protection", is attacked by Jekyll, who wants to kill her to claim vengeance for Mary. Gold can't put a stop to it because Hyde controls his actions; he begs Hyde to stop because Belle has nothing to do with any of this. Hyde points out to Gold that Mary didn't either. Fortunately, Belle is rescued in the nick of time by Captain Hook, who defends the beauty. After a brief fight, Hook accidentally impales Jekyll on a large spike protruding from the ship's mast. Not liking this, Hyde decides to command the Dark One to do something else destructive... only he never gets the chance to do so, because he soon succumbs to Jekyll's injuries and drops dead. Rumple takes his dagger back, and concludes to an uneasy Regina that the only foolproof way to kill a doppelganger, it seems, is to kill the original. Jekyll and Hyde's bodies are then laid out together, each with twin trickles of blood pouring from the corners of their corpses' mouths. ("Strange Case")
Gallery of photographic stills released to promote the character.