Magrat was named as such, because her mother wanted to call her Magaret, but couldn't spell properly. This is why her daughter (with King Verence II of Lancre) is called Princess Esmeralda Magaret Note Spelling. Magrat put Note Spelling on the page she handed to the priest, and he thought it was part of the name. He was mortified afterwards, and Verence and Magrat searched for many ways to change the name, but they were stuck with it.
As a WitchEdit
As a witch, and founder of the Lancre Coven, Magrat was the Maiden, referred to by Granny Weatherwax as a wet hen. She was quite like a New Age pagan, albeit more gentle, and ever so slightly making fun of the whole concept. Magrat believes in occult jewellery, magic knives, songs and folk wisdom. She was better than Granny Weatherwax at doctoring because, while Granny was a better witch than Magrat, because she knew that it didn't matter what type of frog's leg or eye of newt you used, it could even be a piece of grass, Magrat knew that it did.
As a QueenEdit
Magrat grew fed up of Granny Weatherwax ordering her around and interfering in her life, especially when Granny convinced King Verence II to plan her entire wedding behind her back and without her consent. She gave up on witching, abandoning all of her various magical trinkets in the River Lancre. She agreed to go along with the wedding just to spite Granny, though when she found out the extent to which Granny had interfered she called the whole thing off. She helped repel the elves' invasion of Lancre by using old iron equipment and a non existent queen as inspiration.
When Granny Weatherwax retired from witching, Magrat was forced to become a witch again, rejoining the coven in the role of the Mother.