Personally, I think it's a new kind of TF2 crate, and when Twilight pays $2.50 for each key, she can open the box and find a stupid-ass hat.

On second consideration, it might be a BFTC. You never know.

2253416 obviously it's a dick
because that's the only thing anyone ever puts in a box anymore

2253416
I think it's an unholy magical artifact that Twilight and Luna will steal in the S4 finale and use its power to kill Celestia and Cadence.

They will then take over Equestria and rule alongside one another in a dictatorship

2253416

I'm pretty sure 2253424 is in the box

2253425

ITS SATAN

SATAN IS IN THE BOX

2253442
Twilight and Luna are going to become the masters of Satan and use his power to take over Equestria and kill Celestia and Cadence.

Now that is a finale I'd like to see.

2253448

[youtube=www.youtube.com/watch?v=gHQhlhz-_K0]

Edit: This isn't the video I was going for, but it works just fine.