The operating AI of Ledo's mecha (Machine Caliber), assisting him both in and out of combat. Chamber is a highly advanced computer with numerous and sophisticated functions. It can follow whatever Ledo orders it to do and then act independently. Chamber's primary duty is to assist and guide Ledo at his tasks which includes allowing him to fit in with the crew of Gargantia. Chamber's intelligence borders on actual sentient thinking but it has difficulties to understand emotions or acts that defy logic. In addition Chamber's behavior and programming was made to fit the views of the Galactic Alliance, views that are radically different from the humans on Earth. Albeit just like with Ledo, that view will gradually change as the two adapt to the life on Gargantia.
In the end Chamber seemingly does develop full sentience. Caring too much about Ledo's wellbeing Chamber ejects its pilot and engages the enemy Machine Caliber Striker to a last duel.