In the book, Lady Gremlaine is described to have tan skin, dark, smokey eyes, shiny red lipstick and wild black hair barely cooped by a turban. She always wears lavender.
Lady Gremlaine is described as 'tall' in the book.
It is unknown who Lady Gremlaine's parents are. Lady Gremlaine has a son named Rhian. King Arthur is the father of her son. She tried to keep Rhian a secret because she didn't want the world to know. Lady Gremlaine realised that meant that her son was the eldest, therefore he would be king one day. Lady Gremlaine hid him also from King Arthur, so he never knew what happened.
Lady Gremlaine had a brief romantic relationship with King Arthur of Camelot. They had a baby together, named Rhian. King Arthur didn't know that Rhian even existed, and so he thought that Tedros was his first, and only son.
Guinevere and Lady Gremlaine hated each other. Lady Gremlaine loathed her because she felt jealous of Guinevere's relationship with King Arthur. Guinevere hated Lady Gremlaine because Guinevere felt threatened and intimidated by Lady Gremlaine's closeness to her husband (e.g, flirting in public, cozying up to him, trying to get a kiss, always at his side).
Lady Gremlaine loved her son, although these feelings were not returned. She was killed by Rhian.
Lady Gremlaine had no feelings for Tedros, although she was acting as an advisor for him to get through his coronation, wedding, etc.
Lady Gremlaine didn't particularly like Agatha, and during the period of time in which Agatha had to prepare and plan the wedding, Lady Gremlaine took control of Agatha's life, with schedules for wedding planning. Whenever Agatha questioned or talked back to her, Lady Gremlaine would fire back a frosty response.
Lady Gremlaine wasn't a big fan of Lancelot (since he betrayed King Arthur). She branded him as a 'traitor' and at the coronation, she tried to talk Tedros out of displaying Guinevere and Lancelot to the public. When she realised that Tedros hadn't been listening, and he was going to reveal Lancelot and Guinevere, Lady Gremlaine leapt out of her seat but it was too late.