Merlin is the Boar's Sin of Gluttony of the Seven Deadly Sins. She is regarded as the greatest mage in Britannia. Her Sacred Treasure is the Morning Star Aldan, a floating orb she can summon at will and often uses in conjunction with her spells and her inherent power Infinity. The name "Merlin" is actually an alias as her true name is unpronounceable to humans. Ten years ago, Merlin wore a full set of armor with a unique helm that resembled a beetle, like the rest of her fellow Seven Deadly Sins. This armor set had a long dress, and she wore high-heeled boots. Merlin's wanted poster depicts her as a young woman with long dark-colored hair. Her Seven Deadly Sins tattoo is located on the left side of her neck and is colored red, hence her nickname as the "Crimson Pig". Ten years afterwards, Merlin was first seen wearing a long violet cloak that covered her whole body and her face, making her sex ambiguous. When the cloak was ripped apart, Merlin was shown to look very similar to her appearance on her wanted poster. She is seen as a tall, slender, attractive, and light skinned woman with three beauty marks below her right eye (though after her reappearance after Hendrickson's defeat, she appears to only have a single, lower-placed, larger beauty mark). Her outfit consists of a highly revealing and open fur collared long coat, with heart shaped buttons, short shorts that resemble panties with a heart on it, and thigh high boots. Merlin's hair is at shoulder length and black. After having her magic seal spell reflected back by Chandler's Full Counter, it is revealed that her true form is that of a child. In this form, she is described as an adorable child by Chandler with long black hair reaching her mid-back. At the end of the Demon King arc, Merlin was left with burns around her chin and mouth. She herself decides to keep the burns as a symbol of Escanor's existence after he died. Prior to the Seven Deadly Sins' supposed betrayal, Merlin demonstrates a playful nature telling her teammates that their meeting with the Great Holy Knight might turn out to be a scolding from their superior for destroying the Great Druid Altar. Merlin is also apologetic in asking for her captain's forgiveness for knocking him out. She enjoys mocking and challenging others, teasing her apprentice Vivian for losing herself in rage again. Merlin tends to use anyone as a magical guinea pig to test out new techniques she learned so long as the results are good (as Meliodas had noted). Merlin is a very calm and passive woman almost never losing her cool regardless of the situation. Even as she and everyone were being overwhelmed by Galand, Merlin remained calm and was able to think of a strategy to counter him. The only time she loses her calmness is when the situation is beyond her ability to cope such as Meliodas reverting to his previous self or when Arthur was impaled by his own sword. Merlin is described as a very mysterious woman as many who know her have a difficult time telling what she is after. She expressed excitement when the Ten Commandments were free, primarily knowing she could gain a large amount of information from their appearance and taking an interest in Escanor's powers due to the many mysteries surrounding him. According to Meliodas, Merlin tends to take an interest in anything that is considered "rare" such as Escanor's powers and various Demons she can use for her experiments. Even Demons have a hard time understanding what she's after. Despite her mysterious nature, according to Escanor, Merlin is a very kind and cheerful woman. She is normally kind and polite to everyone around her, even those she does not know. Merlin is also the only person who treats Escanor as a person rather than a monster as everyone else does prior to him joining the Sins. She also has a motherly side, treating Arthur as a mother would a son and was deeply saddened over his death. Despite her usually kind and calm behavior, Merlin knows when to be serious. As when regarding the revival of the Commandments, she scolded Hawk for taking the situation lightly. She also took command after Arthur was killed refusing to let anyone else she cares for to die. Merlin loves knowledge above all else. Because of her desire to learn everything, she suspended her own age to have all the time in the world to study and learn everything. For that reason she regularly takes excitement whenever she has the potential to learn anything she does not know about. She was interested in Escanor primarily due to his unique powers as well as how it fluctuates during the day and studies a captured Grayroad to learn more about how his Commandment works. Because of her desire for knowledge, Merlin is a very shrewd and intelligent woman being able to calmly assess the situation at hand no matter how dire it is as well as explaining the mechanics over any form of creature or magic by heart. However, Merlin is not above acknowledging when she does not know something or when a situation is beyond her capability to understand. Despite Merlin being usually calm and serious, she is capable of being shocked or embarrassed. As when Elizabeth regained her memories she asked Merlin if she could call her "Big Sis-Sis" like she used to which left Merlin deeply embarrassed. She even was embarrassed when the others Sins (mainly Escanor) asked if Elizabeth could talk about it more. She appears to have very little modesty, as Merlin has no problems wearing very little in public or even allowing Escanor to give her a massage while she was taking a bath.