I'm so sad, that I came late to the guessing Party. Much less fun if there is an entire book already.
I how ever think he killed her with Twin Stars in previous life and it made the blade shut down
Okay, author. You said that you like hearing our theories...
I'm sure I'm way off but I just connected two things in my head.
1. Scars over his heart
2. Swords that feed on blood
𤨠Is there a connection here?