[X] Har Ganeth, City of Executioners
[X] [Strong] Ghur, the Brown Wind of Beasts
[X] [Strong] Ghyran, the Green Wind of Life
[X] [Weak] The Lore of Fire
[X] [Weak] The Lore of Death
Okay, hear me out here.
Har Ganeth is an excellent pick for a Covent that's basically a bunch of misfits and loses who've ended up in a place where the local power doesn't trust them, they've got to deal with those catty witch elves, and the sorceress cast list is small enough that our protagonist can personally know all the ones locally and they're in a situation where they may dislike each other, but they have to back each other up in the face of those damn fanatics of the Cult of Khaine.
As for the magic, may I present the concept in two words; Goth Hippy.
Like, she wouldn't put it like this, but this is a woman who if born in another life would have been a genuinely happy and content handmaiden of Alarielle over in Ulthuan. Instead, she's an evil sorceress.
And so she channels her natural tendencies into growing thorns to wrap around her tower, cultivating poisonous blossoms in her garden to give as gifts to people who want access to poison, having a menagerie of monsters who show up when she sings like the world's worst Disney Princess, and engaging in horribly unethical mutative works on creatures to make them even more goth and murderous. Like giving her pet black cat wings so it can fly into trees and eat birds. And giving crows the ability to sing so beautifully that people break into tears so the crows can eat their eyes.
(She's bad at the traditional sorceress activities of "I set you on cursed fire" and "I blight you with death", both as part of this theme and also so she has a chip on her shoulder about it and can try to argue that an army of murderous wildlife is just as good as a fireball, just you wait!)