Kell's silver knife is a dagger in which the initials "K.L." are engraved.
The knife is the only item Kell Maresh owns from the time before his memories were sealed and he was brought to Soner Rast upon being adopted by Maxim and Emira Maresh. It is unknown if the dagger was originally Kell's and if the initials are the initials of his birth name.
After his adoption, Kell always kept the dagger close to him. He uses it to cut himself and draw blood in order to use blood magic.