The Margrave

The sorceress-queen Kallista began her rule in the north Hibernian city of Kalin early in the Cycle of Leaves. Her reign was one of dark magic, ritualistic sacrifice of innocents, and her own burgeoning power. Recent evidence discovered by adventurers suggests that Kallista was not truly the Margrave, but that the Margrave was a Ereshan spirit of immense power who crossed to the Mortal World to enact a scheme beyond the People's imagining.
Kallista herself was a tiefling woman who lived and worked in the marsh-like area near the then-town of Kalin. She was a hedge-witch of small power but clever mind. It appears that she had some amount of ambition and cunning, as she tricked two heroes into helping her secure the heart of a black dragon for use in her magical spells. This was only the beginning of her scheming. Over the years, her power grew, and somewhere between her obtaining the dragon heart and her entering Kalin with an army of spirits, she came into contact with the spirit of the Margrave. The connection she possessed with this ancient Ereshan monster is one not well understood by today's historians or mancers, but it must have increased her magical capabilities immensely. Whatever the nature of this bond, it enabled her to become one of the greatest tyrants of all time.
Whether or not this is true, it seems impossible that Kallista was able to succeed in her meteoric rise to power without help from somewhere. A relatively unknown hedge witch became a dominant force of black magic and witchcraft in too little time. Regardless, Kallista appears to have died in a catastrophic explosion that claimed the lives of her servants and, very possibly, several agents of the Silvan Eyes. Her palace in Kalin appears to have been the epicenter of one of the great battles of the Second Looking Glass War, and it seems unlikely that she survived, especially because she has not been seen since.
The Margrave, though, if she truly exists, cannot have possibly accepted defeat quite yet.