Merlock is an anthropomorphic wolf sorcerer who possesses a magic green talisman that gives him the ability to transform into (non-anthropomorphic) animals, including a hawk (a form he most commonly uses to get around over long distances), a vulture, a rat, a cockroach, a griffin, a bear, and a cougar. When placed on the Genie's magic lamp, the talisman grants Merlock an unlimited number of wishes to be granted, instead of the usual three for everybody else. When he first possessed the lamp, some of the sorcerer's wishes that were unwillingly granted by the Genie include his own immortality, the sinking of Atlantis into the sea (which, in this case, was not just a city but a luxury resort that was so popular that Merlock failed to obtain a hotel reservation), the eruption of Mount Vesuvius due to Merlock's hatred of Pompeii, and the creation of anchovy pizza.
In the movie, Merlock is obsessed with retrieving the Genie's lamp, which he apparently lost to the thief Collie Baba (a parody of Ali Baba) several millennia before. Collie Baba buried the lamp, along with a large amount of treasure, in the middle of a desert. When Scrooge McDuck and his family came searching for that very treasure, Merlock with the the aid of his henchman, an Arabic explorer named Dijon, attempts to use Scrooge's ambition to obtain the lamp for himself.
In the end of the film, Merlock finally combined his talisman with the Genie's Lamp once more and wishes to transform Scrooge's Money Bin into his gloomy flying castle. Scrooge and his nephews confront the sorcerer who merely wishes Scrooge to be blown overboard. Scrooge's nephews manage to get the lamp and toss it towards Scrooge so that he can wish to save his life.
Merlock turns himself into a griffin and recovers the lamp from Scrooge, who grabs him and smacks him repeatedly with his cane, making him lose the talisman (thus turning back to normal) and apparently fall to his death. At the end of the film, when Genie was freed, Dijon, whom Merlock wished Genie to turn into a pig, turned back into his original form. This indicates that all of the other wishes previously granted by Genie, including Merlock's wish for immortality, were also undone.
Merlock makes another appearance in the video game Legend of Illusion starring Mickey Mouse. How the game is related to the DuckTales movie, and if so how did he survive the fall is currently unknown. In this game, he is known as the Sorcerer of Darkness and is responsible for stopping the River of Time and threatening the Tree of Life in the process. Mickey Mouse must defeat Merlock in order to restore everything to what it once was. He mainly uses fire and lightning to attack. Eventually, he will change into a dragon, changing his strategy entirely. He will breathe fire at Mickey, fly to the other side of the screen, and toss a spiked ball in front of him.
Merlock also appears as the main antagonist in the video game Donald Duck: Goin' Quackers. Once again, the game's relation to the movie is unknown. He captures reporter Daisy Duck after she infiltrates his temple, and Donald Duck sets out to rescue her. In the final level movie, Donald Duck reaches Merlock's lair, and the final battle between him and Merlock begins. Merlock has three attacks. The first one is to make the floor tiles disappear. Second, to unleash arrows, and the third is the fire attack. In the end, Donald rescues Daisy.
Merlock is a highly sly, dastardly, impatient, strong, influential, foxy, duplicitous, unfriendly, dishonorable, conniving, powerful, devious, stingy, cruel, mean, serious-minded, intelligent, nasty, wicked, self-absorbed, uncaring, roguish, sardonic, and conceited sorcerer. Like many sorcerers, Merlock is power-hungry and egotistical, so he seeks dominance over everyone which carries out by the harsh way he treats his minion named Dijon, using threats and verbal abuse to keep his loyalty in check but in the end it proved to be his end when Dijon used his wish to ask for a fortune and betray Merlock. His obsessive nature and ruthless pursuit for the Genie and his unlimited wishes show signs of a mental health disorder. While in control of the lamp, Merlock becomes a power-crazed madman such as sinking the Atlantic into the sea, the eruption of Mount Vesuvius and the creation of anchovy pizza. In his final moments, Merlock showed to be highly reckless as when Scrooge McDuck fell out of his flying fortress and he transformed into a griffin to reclaim it once again but him losing his talisman mixed with his greed attributed to his demise.
Merlock is a portmanteau of "Merlin" and "warlock"; since Merlock is an evil sorcerer, it is fitting.
Merlock is comparable to Rasputin from Don Bluth's 1997 animated film, Anastasia, as both are sorcerers with long term goals who abuse their minions that turn on them and reform. Rasputin is also voiced by Christopher Lloyd.
It is possible that he survived the fall since he wished to be immortal.
Merlock is the most evil villain in DuckTales, as he is shown to have no redeeming qualities. He is also no problem of trying destroy anyone that stand in his way and forcing Gene the Genie to do the worst things.
Merlock is similar to Jafar from Aladdin; they seek to acquire the Genie's lamp and use it to obtain unlimited power.