Sanguine Dagger

Full Item Description
The Sanguine Daggers were crafted by a now-defunct brotherhood of assassins; the blades, cold-forged from iron ingots, were hammered long and thin, with a keen point and razor edge, the better both to hide against their bodies and the better to pierce the flesh of their targets. The hilts were bound with dark leather, the whole weapon in shades of brown and grey, with nothing to identify them to any who might chance upon one.
That was long ago; now these blades of these ancient weapons have acquired a permanent stain, the hues of blood both fresh and dry mottling across metal and leather alike. This hue has become the mark of these murderous weapons; never forged with intent to be magical, their history has granted them certain foul traits instead.
History
Crafted to serve as weapons for a brotherhood of assassins, the Sanguine Daggers have had a long and violently bloody history; originally forged in a set of thirteen, one for each of the assassins, seven have been destroyed over the years. Those which remain have slowly awakened as, time and again, they were used to end lives in secret, their blades forever stained by the lifeblood of those they have ushered into death's quiet embrace.
The Sanguine Daggers have ended kings and beggars, heroes and scoundrels. They exist only to kill, and care not what purpose the deaths serve. One was used to murder the noble Prince Josiah in his bed the night before his wedding would have taken place; another was used by the Prince's distraught betrothed to murder the assassin who had killed Josiah, the blood staining her hands condemning her when she was found weeping on the Prince's corpse, the bloody blade laying by the wall. Another time, a pair of the blades were traded back and forth, depopulating a pair of noble Houses until the last survivor of the feud took his own life is grief. Another resided for years in the hands of Jack Redhand, a notorious serial killer who left bloody handprints on the stomachs of his victims.
Inevitably, whenever a Dagger's wielder is ended, everyone seems to overlook the weapon itself as they cart the body off, until someone else chances along and finds it waiting to be used again.
Magic/Cursed Properties
-Wounds inflicted by a Sanguine Dagger heal poorly, if at all, and bleed heavily. Even magical healing seems to have minimal effect.
-When being concealed, a Sanguine Dagger will tend to be overlooked, regardless of how poor the concealment is. A guard specifically searching for one will be likely to find it, but a cursory inspection will most often fail to unveil it.
-The daggers have a kind of foul empathy, amplifying the wielder's most murderous thoughts and desires, egging them on to follow through on them.
-Once a person has killed with a Sanguine Dagger, they can never be rid of it, nor of the blood that is now on their hands. Scrub though they may, their palms are stained forever, and even if they hurl the dagger off a bridge, they'll find it waiting for them wherever they next pause to rest.
Plot Hooks
-A series of murders have begun in the city the PCs reside in; the instrument is one of the Sanguine Daggers, and all the victims seem to have bled nearly dry despite their best efforts to staunch the wound. Who is next? Perhaps someone the PCs know? Perhaps one of the PCs themselves?
-One of the bloody blades has fallen into the hands of the party; what will they do with it? Can it be destroyed, or perhaps purified? What if they're attacked, and the dagger is the closest thing to hand?
-A historian is seeking out the Sanguine Daggers, having pieced together their history; his first goal, historical curiosity, is swiftly overshadowed by the foul empathy of the blades he recovers.
-A new brotherhood of assassins has been born, and each of the six core members bears a Sanguine Dagger. It's up to the PCs to stop them before things get out of hand.