Shahmeran
The Shahmeran has lain bound beneath the Basilica Cistern since the days of Justinian and Theodora, the last battle against her and her spellcasters having been fought in that same age. Alemdar Mustafa Pasha of March started sharply when the name "The Shahmeran" was spoken, betraying no ordinary measure of concern at the mere mention of her.
A red-gowned prisoner in that same undercity gaol once professed herself the Shahmeran, and the party loosed her upon the strength of it — but she proved a counterfeit: a sorceress who had merely played the part, and who, once freed, turned upon them, working Jean-Zera Mongé into a goat and striking out with a death-dealing glare before the party put her down. The true Shahmeran, they learned, remained sealed behind the prison's stoutest door.
Behind that great anti-magic door the party met at last the true The Shahmeran: an enormous serpent-woman, twelve feet in height above a vast coil, held taut by runic chains at the four corners of her cell in a wash of pale green light. Imprisoned since the reign of Emperor Justinian and Queen Theodora — whose magi had subdued her after she raised great magic from the earth to defend Constantinople against Justinian's conquest — she offered the party her aid in exchange for her freedom. The bargaining was perilous: she plunged the chamber into magical darkness, turned Sidra al-Najjar into a lizard, and so turned aside their spells that each rebounded upon its caster. In the end Miray Ruba Mata Biru and Sidra al-Najjar broke two of her four chains, and she counted the bargain kept. She then decrypted Osman's Journal — a Lodge cipher no other reader had cracked — revealing that Mira, sister of Haseki Sultan Bergüzar Hatun, is a diviner whose living presence mutes the Sultan's full power, and giving up the place where Mira might be found. She warned against suffering Bergüzar to become another Theodora, urged the party to keep Mira alive, and told them they might reach her again by asking Sidra's djinn. She remains but partly freed — two chains broken — beneath the Basilica Cistern.