She doesn't rule Ustalav, but she's the closest person there is.

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Records recount Lord General Haldrian Ganailad of Lastwall saying of Countess Caliphvaso, “Her ladyship is all that is Ustalav. Ambition’s flame burning atop a taper of poise and undeniable charm, wholly cloaked in a midnight of unspoken temptations.”
... Yet despite such fears, rumors endlessly surround the vain but lethally alluring “Queen of Caliphas,” most relating to her supposedly scandalous relationship with her nephew Renies the disappearance of her sister Millaera, an alleged penchant for criminal decadences, or the fact that Lord Ganailad’s flattery was recorded more than 50 years ago.