Circaea is the daughter of Prince Brand of Amber and, it turns out, Ashanah of shadow B'leth-Shine, Brand's beloved wife. Unfortunately, Ashanah was killed in an uprising on B'leth-Shine engineered by one of the other Elders, which began Brand's long and bitter slide into madness. And so for her own safety Circaea, a baby at the time, was hidden elsewhere in shadow by Brand...
However, as far as she knew up until the age of ten, Circaea was the orphan of upper-class parents in the world of Verantium who had been killed in some far-away war when she was very young. Verantium is a shadow very like late-Victorian England, but with magic - which is solely the province of the upper (ruling) classes - instead of technology. Upper class men and women are both taught magic, but women are really only expected to use it to support their husbands and families.
So as an upper-class orphan Circaea was raised and schooled in the Orphanarium, a great dark gothic-style dark stone building located in the Verantian capital city of Lanchaelis. This was essentially a large, harsh boarding school with no holidays and very harsh discipline. She was taught all the things a young woman of the ruling classes should know - magic, etiquette, history, the classics, running a household, and so on. But because she was always tall for her age, a bit strange-looking (with silver-white hair, pale skin and pale blue eyes), and superior in both physique and mental strength to all of her peers she had no real friends and was lonely most of the time, wishing for escape, or at least a friend.
She might never have known of her Amberite heritage and gone on to an unhappy married life in Verantium but for the arrival, on her tenth birthday, of a book entitled 'The Young Lady's Illustrated Primer'. Apparently it had been sent to her by her long-dead father, but had been lost in the postal system of Verantium until now. At first it looked like just another tedious tome telling young ladies how to behave. But then, when she was alone, its pages became animated and it spoke into her mind, telling her things. Wondrous things. About other worlds. Amber. Her true heritage. Her true parentage. Freedom. And, in time, the means to attain that freedom via the power of Trump (that she could learn now) and, in time, of the Pattern.
She spent long hours, in secret, late at night and in odd corners of the Orphanarium, learning from the Primer. Unavoidably, it subverted her away from the rigid ideas of her place in Verantian society. And equally unavoidably, this led to harsh punishment when her 'wrong-headed' thinking was discovered. The Primer was taken from her, to her great distress.
Then, to her amazement, it reappeared back in her hiding place for it. She continued to learn from it, despite discovery and repeated confiscation of, and even attempts to destroy the Primer.
And by the time she was eighteen she had mastered all the lessons the Primer appeared able to teach, including those relating to the creation of Trump, Blank Trumps, and Imprints (which the Primer seemed to think were necessary, and without which, it is true, her freedom would have been much harder to attain). The Primer hinted at Trump abilities beyond those it had taught her, but seemed to know no more, leaving them 'as a lesson for the student'.
And when she had learned everything it had to teach, the Primer seemed to become inactive, reverting to the plain, dull, tome it had appeared to be when she first received it, years before.
But using what it had taught her, Circaea escaped, first from the Orphanarium, then from Verantium itself, and out into the shadows beyond. Although it seemed to have lost its power, the Primer was one of the things she brought with her, for its sentimental value if nothing else.
The first weeks and months of freedom were hard - the Orphanarium had hardly trained her for such things, and the Primer could only teach her so much without her having any chance to try and see things for herself - but she survived, and the freedom she had now more than made up for the hardship. The first time she dared to wear trousers was, in particular, a turning point.
As she went she learnt to fight, to love, to hate and, when necessary, to kill. She built herself her bracer as what she considered a necessary defence and a means to store her spells. She also learnt about the ways in which things work differently in different shadows, and about technology as well as just magic.
Although she was not affected by it, not having walked the Pattern, with the sickness affecting those who had she was found and discovered as an Amberite, and came to Amber for the first time. It was here that she learned the tale of Patternfall, and the fate of her father, as well as the fact of her having a brother - Rinaldo. But when, because of her parentage, she was told that she could only walk the Pattern under restricted circumstances she vowed that she would not stand for such treatment and would only ever walk it unrestricted, or not at all.
She returned to shadow. She made some attempts to locate or contact Rinaldo, but without success.
However, now knowing more of Amber and its low opinion of Brand, and now that her existence was known, she felt the need for a secure home base, and perhaps additional sources of power.
She found shadow Ensilaram almost by accident, seeking a home base shadow. She was able, by means of money and her obvious powers and skills, to take over a small abandoned duchy, the Duchy of Justicia, and make it a success. She did not really have too much ambition in the shadow as it was already pretty much what she wanted, but then the old Queen, Mehitabel, died and the chance for her to take over the shadow arose in the competition to elect a new monarch. She won the competition to do so, and so she became its legitimate ruler, the new Queen of shadow Ensilarum. This was a good thing, really, a reversal of her lessons in Verantium.
Using her powers over Trump and magic, and some hints from the Primer, she also built her sentient Umbrascope (shadow scanning scope), Cerebaton, which in addition to helping her with Trumps of desire has, on occasion, also proved useful in keeping her safe in other ways.
Since becoming Queen she has fought other duchies, traded with other shadows, and seen and done quite a lot out and around Ensilarum.
She has been the Queen of Ensilarum for quite a long time now, and though she takes her Royal responsibilities seriously she is nonetheless beginning to find things to be a little bit boring. An opportunity to do something new, or to act outside Ensilarum might be quite welcome...
She is familiar with the Patternfall war. She has heard that Merlin, son of Corwin did something damaging to Castle Amber itself and was for a very short while Banished. She knows that Dworkin himself ordered Random to rescind this and that Merlin is currently in an insane asylum in the courts of chaos.