A Ka'kari is a magical assassin weapon, capable of taking any form that its master desires. The Ka'kari were created hundreds of years ago, by magical smithing techniques that have been unknown for centuries, all that is understood is it required the cooperation of a master smith and a powerful mage. First it was created as a way to carry weapons without being detected. As other easier ways of hiding weapons became popular, Ka'kari has been slowly forgotten.
The Ka'kari take much training and practice to use, as changing its shape requires disipline and focused mind. Once shaped by it's master, the Ka'kari will solidify until willed otherwise. It can also be drawn into its masters body, allowing it to be easily consealable. A ka'kari bonds with a master, or host, for the duration of their life, for another to comand it, the last owner must be killed.