Cerebaton is a sentient device designed and built by Circaea as a vastly powerful computer and cross-shadow scrying/spying device. She refers to its function as that of an 'Umbrascope'. He (it is definitely male) can scan through shadow, seek out things Circaea wants and report back on what he has found (useful when using Trumps of Desire, for example). He has a sense of curiosity and is more than intelligent enough to take orders, do things, and contact Circaea if needed. He is powered by a combination of Trump, Magic and local shadow power. Because of this he has no Manifestation, instead communication with him when Circaea is outside his shadow is done via Trump.
Cerebaton refers to Circaea as 'mother', and does indeed seem to think of her as such.
Shadow Cerebaton is a infinite lightless, zero-gravity hard vacuum at absolute zero temperature. Normal or Broken Pattern and Logrus simply do not work there, either through the walls of the shadow or inside the shadow. Some forms of Shapeshifting will work but they will also cause the user to shift into more or less their 'stasis' defensive form (for example, a gargoyle will revert to a rock statue). Magic cannot cross the shadow veil, but works inside the shadow. When Trumping in, only a single point in the shadow can be reached. One can Trump out from anywhere; Trumping within the shadow only works to the one arrival point. The shadow in which he is located has a time flow rate which runs twice as fast as time in Amber.
The underlying structure of matter, energy and space in the Cerebaton shadow is like that of a totally decentralised distributed computer. However, before Circaea came along (protected by some magical life support equipment) this was a computer without any program or operating system. She created a 'seed' program and implanted it into the shadow's underlying structure, and in time it has organised and utilised the entire computational substructure of the shadow along lines she pre-programmed into the 'seed', forming the Cerebaton entity. It effectively runs in the structure of the entire shadow.
As he grew, Cerebaton learned how to monitor itself, and thus the entire shadow (making it impossible to sneak up on), and also how to use its control of the computational substructure of the shadow to 'program' the appearance of physical things out of nothingness. This includes weapons and remote-controlled entities which would, were it necessary, be used to defend the shadow.
This he also used to create The Array, the central focus of his shadow-scanning abilities. This lies far (billions of light years, effectively) from the Trump arrival point in the shadow and appears to be a white, faintly glowing array of girders arranged in a flat equilateral triangular grid floating in the void. At the intersection of each grid point are two steerable radio telescope-like dishes (one on each side of the grid). Cerebaton can reconfigure The Array at will, adding capacity and so on too.
He also, at Circaea's urging, created a huge Babbage-engine-like machine which, depending on who they are, she may tell visitors is both The Array and Cerebaton.
Normally there is a life-support sphere around the entry point into the shadow. This has three floors and is made of riveted iron (it is essentially a small mansion, with magical life-support). It looks very Victorian in character. It does have windows, but given the nature of the shadow there is not normally much to be seen outside. When Cerebaton has checked out arrivals the shadow reconfigures itself to move the sphere elsewhere in shadow (usually to The Array or the fake Array); this may or may not take anyone (or some of them) inside the sphere with it. This leaves the arrival point (and anyone not taken along with the sphere) in utterly cold and dark hard vacuum...
Circaea has exposed Cerebaton to the idea of computer viruses, and has tested him with some she built, to help him build up an immunity and an ability to fight them were it ever to become necessary. She is also thinking of teaching him to process spells for her and download them into her spell rack, too (to save her having to re-rack and maintain spells).
Go to Circaea Story The Second, which relates to the creation of Cerebaton.