Both of the Sister Blades, Mercy and Cruelty, are almost identical in craft. The blades have a silver handle, composed of strings of an unknown and presumably magical metal that shows no sign of wear or age. Coming from within this unique handle is a thick, silver blade that according to legend, slices through air when swung.
Along the side of both blades is the following phrase, written in the Runic Alphabet:
"Through war and peace, the blades of the merciful and cruel will forever be tainted and empowered by the souls of the executed."
The most obvious form of magic found upon The Sister Blades is the presence of runes that seem unique to these weapons alone. When written in another context, these runes show no power. These runes are told to empower the weapons, becoming sharper each time they kill a mortal. When an innocent mortal, animal or man, is killed with Cruelty, the runes shine emerald and the blade flashes briefly. Similarily, when a sinful mortal is killed with Mercy, the runes shine white and the blade also flashes.
It is also said that Cruelty is more effective when fighting the innocent, while fittingly Mercy is stronger versus a guilty being.
Besides the magic of the runes, the blades never seem to dull.
It can be assumed that the two Sister Blades are of Woven craft based on the writing etched into the blades. The exact date that the blades were forged aren't known, but it can be safely assumed that they were crafted after the year 1046 in the city of Krybain.
Through time, the blades made their way into the hands of the Ja'mor Dynasty, a nomadic army who inhabited the treacherous Kismoor Basin of northwestern Vash Prime. The Ja'mor Dynasty slowly took over many former Woven cities, including Darkscape.
The last Ja'mor wielder of the blades was Ekoe Ja'mor, who was slain by the young Alliance of Vae in the taking of Darkscape. The sister blades were then stored in Darkscape for just less than a century until the awakening of the lich known as Shi Kotari. Upon awakening, Shi Kotari managed to acquire the blades and ever since, they lay in his undead grasp.