The murder knife is an optional dialogue device used to dispose of certain characters abruptly. It is a knife in the Warden's, the Warden-Commander's and Hawke's possession that they use outside of combat, regardless of class. It does not need to be equipped and does not exist in the inventory.I took Vmachinas original and rescaled it to fit the hand nicely. (http://dragonage.wikia.com/wiki/Murder_knife)
I also changed the mating pin so that the blade slots into the handle and recut one of the runes.
Finally it's been split laterally so that both sides look good on printing. In PLA use superglue to join the halves. Acetone welding should work in ABS (though I havnt tried it.)