Ms. Liberty - Incarnate?

You're right, she cannot draw it from the scabbard. But there's nothing saying she can use both the scabbard and sword to beat you clean thru to China.

I seem to recall this book is pretty much hated for the fact that everybody is relegated to a single origin again. Much like the Origin of Powers arc saying everybody is Magic typically being treated as "ignore it" when someone complains/asks.

Alien, hell, Kheldian? Pandora's Box or Magic.
Trans-dimensional being or again, Kheldian? Still the Box and/or Magic.
You built a frankengun or some sort of armored suit? Still the Box or Magic, because you weren't smart enough without it.
Rikti Magus? Well, they scientifically studied their weakness, reverse-engineered it, then proceeded to master using it...but it's still Pandora's Box or Magic somehow doing it itself! Asinine.

That said, I try to interpret the Pandora's Box thing as being either a catalyst (as though it massively influences chaotic circumstance..whatever) or just acts as a source of people like Statesman.

Considering what the scabbard of Excalibur is supposed to do for you, I'd pretty much just leave it on my belt and not risk losing it.

Web of Arachnos doesn't use the box as the source of anyone's power other then Statesman and Recluse, in fact Dark Watcher has his powers before the box is opened. It functions not as a power source but rather as a power drain, explaining why characters previously didn't make use of their powers.

She's the diet coke of Incarnates?