A small device that can be used against commandos. This device was a reward for doing a chapter of the merovingian missions (Episode 4.3?). You were given some EMCP codes which you then took to a collector who would give you 15 devices.
These devices are deadly when used in a room full of commandos as they cause 9,999 damage to all commandos, no matter what level you are or the commandos, so a level 2 player could use one to take out a group of level 50 commandos.
Since these were given as a mission reward and the mission is no longer available unless you have a device or the code for it, then you will need to hunt out someone who is willing to sell them on.