I am having thoughts about Xin Mo and the Xuanwu sword today that I can't get out of my head. They are so similar to each other minus Xin Mo's teleportation ability that it makes me think they could be the same sword but in different timelines or just hundreds of years apart from one another.
What if the Svsss/PIDW universe is much much later in the timeline and something catastrophic happens and causes the endless abyss and the Xuanwu sword gets trapped there. There would be waaaay more resentful/demonic energy which could make it manifest the teleportation ability.
OR
MDZS happens waaaay after Svsss/PIDW and somehow Binghe lost/abandoned Xin Mo and it came to rest in the Xuanwu of Slaughter. Maybe Wei Wuxian wasn't able to use the teleportation ability because he wasn't as strong as Binghe and couldn't subjugate the sword.
These ideas aren't super thought out, but it wouldn't be the first time MXTX had one sword appear in two of her stories (Hong Jing) and we just didn't realize it's Xin Mo in MDZS because it's not called that by Wei Wuxian or anyone else in the MDZS universe.
