The creation of intelligent magical weapons is not an exact science and there are occasional failures, as such think of causing a little more stress to your players by "rewarding" them with an insane magical weapon
Agrophobic, refuses to come out of the scabbard without a strength check to draw it.
Haemaphobic: afraid of blood, fight at a penalty against any blooded creatures but really good against undead, elementals etc
Schizophrenic, not just one mind in your sword, lets have half a dozen minds in there, all different and bound to cause confusion
the possibilities are endless
The third son of a candle-maker, and secretly a spy, Tsiao Fong Wei betrayed his family, clan, and town to the merciless Qongg Dynasty, causing the deaths of his own family members. He survived to an old age hiding out in the country side and keeping a low profile. One day however, the “Paper Knife” finally found Tsiao Fong Wei , and exacted his revenge on behalf of the folk, dead and tortured.
After a furious struggle, the “Paper Knife” plunged twin burning candles into the eyes of the traitorous old man and laughed, as Tsiao Fong Wei howled in dismay and pain. Some say Tsiao Fong Wei died that day. Others say that the old man somehow escaped despite his sudden anguish and utter blindness.
The truth is lost to time.
But to this day the children of the Red-Ridge County towns and villages are told by their parents to always beware twin lights in the darkness and to never venture into the woods at night, and to keep an ear open for the Groaning Ghost, for somewhere out there Tsiao Fong Wei the Traitor, now a vengeful spirit, stumbles about the darkness moaning and wailing, candles still sticking forth from out of his otherwise empty eye sockets. And though the candles plunged into his eyes all those years ago were a’flame going in, now the wax protuberances are somehow lit from within and burn without, and two flickering lights in the darkness, always portend his coming.