Ken Marlen is an Earth follower.
Before 4Kingdoms (Arc 1)
After about three years, the king of Prielian had heard about the city's resident 'mysterious mages,' and how they were living off magic show revenue. He summoned Ken's father and requested a show, and he obliged. The king hired Ken's father as the official court mage (a very important job, as the court mage protects the kingdom from magical threats like the royal guard defends it from physical ones). After four years in the king's service, Ken's father was somewhat old. Duties of court mage fell mostly on Ken. Eventually, her father moved back into the forest home with Ken's mother who had regained her sanity. As a result, Ken became Prielian's court mage when she was about 20.
Three years later, while wrapping up a mission to defend a village from the Crimson Cult, Ken found a book lying on the ground and picked it up to read it. The next thing she knew, she was in a completely different realm. She found her magic did not work and her Thaumaturgy equipment had dissolved into its component parts, bar her Goggles of Revealing. Ken could not recall how exactly she had somehow traversed realms.
Unfortunately, for a long time she was unaware that she was missing several months of her life back in her old world. She had been infected with a sort of magical disease called Warp following her mission to defend the village, and had done many dubious things while under its influence. Despite forgetting what she did during those months, the Warp’s influence on her personality remained.
In 4Kingdoms (Arc 1)
Throughout her time in the realm, Ken (especially after recalling her time with Warp, after which she became more reckless and easily angry) was prone to being attacked by enemies and friends alike. Ace stabbed her, Euphoria’s alternate personality Demise stabbed her twice, she was put under a sleeping spell accidentally, she was smited by Richard for her association with Ace and was sent many nightmares by him for the same reason, and her daughter Anastasia pushed her off a roof, locked her in a cage, stabbed her, and cut her heel. She did not learned her lesson either - she continued to shout at people she should not, like Richard, believing she could take revenge on those who hurt her family, only to get hurt herself in the process. However, in one instance she was successful. Ken was an accomplice to Ace when he murdered Dimitri Haver after learning that Dimitri brutally murdered Anastasia, though her involvement is not common knowledge.
Death (Arc 1)
Before 4Kingdoms (Arc 2)
In 4Kingdoms (Arc 2)
Ken is of a medium height, with green eyes, and brown hair down to the middle of her back that is usually bunched into a loose ponytail or braid.
Her clothing usually follows a purple and gold color-scheme, as they are the colors she grew up around. During Arc 1, she wore a purple and gold sweater, black pants, and gray boots. She also wore a brown cloth sash around her waist studded with the remnants of magic vis crystals from her old world. During Arc 2, she wears a sleeveless white and gold tunic, black pants, and gray boots. She also wears a green and silver cloak once she became Earth's priestess.
She always wears her Goggles of Revealing on her head, though they are functionally useless. In Arc 1, they somehow escaped being removed from her person like her wand and Thaumometer during the world switch, and so she keeps them on her at all times as a reminder of her home world. In Arc 2, she discovered ancient writings that told her how to make the goggles instead.
Ken does her best to be a very nice person. She tries to give everyone the benefit of the doubt and is a very good friend to have. She is very protective of her friends and family, to the point where she would sacrifice her own safety for theirs. Ken has a tendency to informally (and often formally) adopt younger people in the realm, and naturally has a motherly personality, even if she is not very good at it. When she is angry, however, she is very angry. While weak with a sword (being used to magical combat), she will put a lot of effort into winning a fight. Her ideas of right and wrong are a bit scrambled due to her experiences with the Warp, and this is a sore spot for her.
In Arc 2, she has a bit more outward confidence and is often suspicious of others' motives, which makes her a good law enforcer. However, without the proficiency in magic she developed in the other timeline, Ken never really became confident in herself. She puts on a show, but she is secretly very lonely, and a bit scared, though she does not let that influence her job performance.