I made it myself and carry it on me at all times. The shape allows it to rest comfortably against my arm while I sleep and play. Actually I always keep it on my arm, my right arm generally. Although it also goes on my left arm and leg. But that’s just one feature.
As you can see, the top half is a blade. That blade continues along the pen but stops before the grip, ensuring that it never gets in my way while writing. This discreet blade has come in handy on a few occasions. I keep it on my person at all times for this simple reason.
You may also notice the absence of a fountain and no need of an inkwell. My pen draws blood from its victims. It writes with the blood of its vanquished foes. In fact they don’t even need to be dead, I’ve killed a few men simply by draining them of blood while working on a novel.
Oh, and all it needs is a signature.