Milyastelle.
I think I should explain the inspiration and the root for this name.
That name is a combination of the words "Millennium" and "Castle" but I tweaked it a bit.
As you can see, there's no way I'd just suddenly come up with this name. I saw that you have Ranni the Witch as your avatar, and this reminded me of a short novel I read back then called "Angel Notes". There are rulers dubbed as Six Sisters and they are all witches with a generalized appearance of the witch (pointy hat, broom).
Short story, one of them was killed and the impact created the Great Rift, inside the area, there's a prison resembling a castle called Witch Swift Umbrella which I thought sounded cool, but I found that place is linked to Millennium Castle from a visual novel Tsukihime, it said the former is the "original form" of the latter.
But, but it has a meaning based on my interpretation!
Millennium means a thousand years old, while I interpreted Castle as a building for people and management stuff. I imagine a castle that lasts for or more than that long and hasn't turned into ruins or museum must've been protected by an incredible person or people. So I hope for you a well-nurtured journey in your writing life where you will learn and grow a lot, perhaps you will be the nurturer too in the future.