The babels were an advanced generation of casts created in the Catherion Imprimiture to overcome the limitations of the other generations. The goal was to make a self-aware system that would be linked to the mind of a time-active agent instead of the the Homeworld's noosphere or the operating system of a timeship.
Only about eight were created, and all were incurably insane. One escaped babel massacred almost everyone at House Catherion, leaving only one survivor; (PROSE: The Book of the War) the Order of the Weal subsequently kept it prisoner under House Ixion, where Chatelaine Thessalia consulted with it about the upcoming War. She eventually released it on an isolated planet on the frontier in time, giving herself as its host; it killed her. (PROSE: Newtons Sleep) The other babels were confined in areas where they were deprived of radiation and eventually starved to death.
However, at the start of the War in Heaven, the Great Houses came to regard the babels as a necessary evil. Three were released during the Lethean Campaign, where they were supremely successful wherever deployed and provided the Great Houses with a powerful advantage. (PROSE: The Book of the War)
The babels are pure contradiction. They have no passion for war. They don’t see an enemy: they see meat. Yet unleashed, they become nothing but passion, fury unchecked by mercy or satisfaction. I have seen babels delay an offensive in order to abuse or mutilate a prisoner. They do not like to kill. They take care and pleasure in keeping their victims alive as long as they can. I spoke to one today. Her voice was so sweet and she posed herself with such delicacy. One can almost long to be the enemy and suffer their affections.All three were destroyed when a secretive agent killed their hosts and left them momentarily defenseless to the enemy suicide attacks; The Book of the War stated that, after this deployment, the babels were extinct. (PROSE: The Book of the War)