The C Cube was created by Artemis Fowl, sometime between the second and third books using a hybrid of fairy and human technology (fairy technology was obtained by using the computers in the LEP helmets that Butler acquired from LEPretrieval One in the first book). It is stated by Foaly as being "obsolete underground", although Foaly is unable to stop it from pinging them . The C Cube is fifty years ahead of human development schedule.
It is a red, metal cube which contains an omni sensor that allows it's multiple functions including the ability to read information on any platform, piggyback any satellite, an MP3 player, and also a miniature television that can copy any video and play it in high definition. It also doubles as a phone and a computer. It can also trace any signals from satellites to even LEP signals hundreds of miles underground. In The Eternity Code, the C Cube gets stolen by Jon Spiro, who is unable to hack the eternity code encrypted by Artemis. It is later retrieved through the combined efforts of Artemis, Juliet, Mulch, Holly, the Chicago SWAT team and police, and Foaly.
It's ultimate fate is unknown as Artemis has seemly abandoned his plans form a multinational corporation around its capabilities, it is assumed that due to his mind wipe it is either destroyed or locked away by the People.
The Cube doesn't have much of a personality as it is not alive, but while Foaly is controlling it, it is humourus, sly, and quite rude.