True... well if he really is gone at least he died nobly
It could happen that he comes back. (And I really hope so. I was reading the manga everything was fine and then Break died. I cried so hard and couldn't look at his face without crying for 2 days.) There was a manga that I read once and they just killed off the main character's brother. The near to the end of the manga he showed up.And I think there are many people who read the manga on and on just becaus of him.
*Then
Please come back Break! The manga will be boring and not funny without you!!!
My theory: he was the chain all the time since he had been drowned into the Abbyss and he's the real Mad Hatter. In the manga his chain has no certain apperance, it's just a hat...so this may be the reason. He is the chain created by the Will of Abyss to destroy the Abyss or Gates leading there. So he might come back!!!!
Given how time bending has taken the spot light in the series, it's not out of the question to state that The Intention used Break's soul from his dead body or something to create the Mad Hatter in order to further his promise to The Intention to free her from her title. But we'll just have to wait and see.
You are missing the point of every view.
1. Oath was made, so he can free her from the Core (or rather destroy her), that's why she gave him the chain, Mad Hatter, which is the 2nd in power there, in Abyss (first is B-Rabbit).
2. He wont comeback or rather he doesn't wish for... if he knew the consequences he wouldn't have wish to change the past (part of his notes after revealing of his past).
Chain or not, I just want Break to come back:'(