Best theory I've seen for what's inside the box

It may or may not be correct but it makes the most sense out of the other theories I've seen. I saw it in a comment on one of the TT posts on tumblr when the issue came out.

What's inside the box Damian took from Alfred feels extremely important. It's been built up just based on the reactions the characters give it. So most of the guesses have been pretty big too. But with things like "Jason's memory", "his soul" and the like I don't know how or why Alfred could come into possession of them. Whatever is contained in the box has to answer several questions in a satisfying manner or else the plot was a disappointment.

• Why was it in Alfred's care when Jason says it's his business?
• Why does Jason consider it bigger than the whole crusade?
• Why did Alfred have such a serious reaction to Damian taking it ?
• Why does Damian act like it's the ultimate trump card?
• Why is Jason stunned by Damian having it and then pissed when it's used against him?
• And why wouldn't Bruce stoop so low to use it?

At first I didn't consider how well the theory works. There might be some flaws but it still fits better than other suggestions I saw and it makes you realize how horrible Damian's actions could be if it's true. 

What if it's the ashes of Jason's mother?

• Alfred could be holding it for safe keeping until Jason was ready to spread the ashes. This sort of explains the decorative box although I'm not certain why it had bat symbols on it.
• It's extremely important to Jason because it's so personal. Despite her flaws Jason loved his mom. 
• Alfred would be disgusted and furious with Damian for using the remains of a love one as leverage. He also knows how badly that would hurt Jason.
• Damian would probably think it was an instant win for him if he has a "hostage." It's essentially a weakness to exploit to him.
• I don't think Jason, or anyone really, would expect Damian to do something so awful. 
• Given the loss of his own parents the idea of Bruce ever doing such a thing is unthinkable.

I'm not sure if any flaws I could find hold up well. I do not have much knowledge on ashes but my sisters' cat had ashes about the size of that box. I'm guessing there would be more human ashes meaning the box would have to be bigger. I'm not 100% on this. Also, would Jason risk spilling it when he smacked Damian's hand to send the box flying? This might be explained away if he knew for sure that the lock wouldn't open on impact. Plus there would have to be a bag inside to keep the ashes in.

This would fit but at the same time it would mean Damian really has a lot to make up for. It would also explain why Jason was so brutal too. Honestly I don't know what else would fit and make sense with all the hype it was given.