The weapons have lain in House Jor'akrin since they were forged. Whenever an important assassination is called for, the weapons are used. After one assassination, the assassin attempted to keep the weapons for himself. House Jor'akrin brought its full fury down upon the unfortunate assassin. No one has ever tried to steal it after that.

Abilities
The dagger contains a powerful poison. The poison paralyzes the person once he is hit.  Once a dart is put into the blowdart, it is imbued with a powerful magic. Once the dart hits the target it disintegrates. The target wil feel only a tiny prick. The dart actually sends a giant spider's egg to the target's heart. After three to five days, the egg will travel to the target's stomach. Then it will hatch, killing the host. 

The weapons are phsychically connected to the matron mother of house Jor'akrin. The matron mother will always know where they are and if an assassination has been pulled off succesfully.