The company descended at last into the flooded Basilica Cistern beneath Constantinople, where the air hung thick with the scent of damp stone and the water lapped against the raised wooden walkways, and the dripping echoed with an ominous patience in the dark. Several boats lay scattered about the accessible entrance, their dim lanterns picking out the murk, and two Mansur Enforcers stood guard against further intrusion. Jean-Zera Mongé, however, talked the guards into standing aside upon the pretext of official business. "We've never gone any further than here," one warned them; "I wouldn't necessarily trust the boats, but you're welcome to use them if you wish; just return them when you're done." When Sidra al-Najjar asked what dwelt below, the guard bent to meet her eye. "I can only assume that there are Merrow folk and other strange creatures that live in the waters," he said, "but the only things we have actually seen evidence of are Bichura and Bichura — tiny humanoid-like spirits that are essentially spell residue beings. They can be mischievous, making your life miserable if that is their intent, but individually, they're pretty scaredy and benign."
Passing within, Jean-Zera found a warning cut into the wall in French — "Beware. The danger below. I have lost not just my work but also my beloved" — signed with the initials "PG," which he knew for the mark of Petrus Gyllius, the sixteenth-century French scholar and explorer who had laboured in this very region. The party took torchlight from a nearby boat — "We can take the torches from the boat," Sidra suggested — and she cast a spell to soften the group's tread as they advanced along the uneven boardwalk. Presently she spied a burlap bag dangling off the edge of a platform. "Do you want to see if you can touch it without touching it?" she asked, and Jean-Zera, detecting an abjuration upon the bag, tugged at it with a Mage Hand; finding its weight beyond the spell's strength, he hauled it up by its rope. Inside lay an old but pristine hand drum, its preservation owing to the bag itself, which warded its contents against age and rot; they kept the both of them. Gizem, meanwhile, marked a submerged mirror — a great glass some seven feet tall and three and a half feet wide — lying just beneath the surface, and within it an unfamiliar soldier of East Asian features, in a fur cap with a bow slung across his back, gazing up at her in puzzlement. She waved and named herself — "Gizem" — but the soldier only unslung his bow and watched her warily, giving no word that could carry through water and glass. Miray, studying him, recognised the aspect of a Mongol-era warrior out of old images and descriptions.
The spirits of the place were about them now. A Bichura essayed to pick Sidra's pocket; she rounded and slapped at its hand — "Excuse me. Let's not take things off my body" — but the creature vanished ere she could catch it. Making amends, she offered it a piece of baklava, first by hand and then set upon the boards; after a pause the pastry lifted of itself and drifted away northward into the water. When Gizem in her turn tossed baklava toward the mirror, something thrashed violently below, obscuring the reflected soldier for a moment before the water settled. "That's hungry," she remarked, and the company moved on. They were not far gone when a deliberately weakened stretch of boardwalk gave way beneath Gizem, Sidra, and Miray with a sickening snap — the whole a hunter's trap — dropping Sidra and Miray into spiked water while Gizem kept footing enough to stay mobile, the water there proving shallow enough for her to stand where the other two must swim. Two Merrows surfaced to the attack; but Gizem hauled Sidra back up onto the far side, and a Bichura farther ahead flung a rock past Jean-Zera that struck one Merrow full in the head and badly hurt it.
The skirmish that followed was a near thing conducted amidst the ruin. Sidra tried a Charm Person upon the nearest Merrow and learned at once it was no valid quarry — "That means it's not a valid target, so you attempt to charm it and this is not a kind of thing that can be chunged that way." One Merrow clambered up toward Miray with claws and a makeshift dagger whilst the other loosed harpoons from the water, but neither landed a blow; Miray's own stroke went wide, Gizem wounded a Merrow with her crossbow to prove that missile fire could be answered in kind, and Jean-Zera's psychic assault was shrugged off — even as the helpful Bichura's next stone flew astray and cracked Jean-Zera in the back of the head. Sidra then laid a Sleep upon the nearer Merrow, and it dropped incapacitated before it could stir, while its fellow disengaged and slid beneath the surface. Miray crossed the broken span to safety; Jean-Zera, essaying the same, fell in, avoided the spikes, and climbed out on the far side; and when the last Merrow tried one further harpoon, Miray answered with discordant whispers that wounded it and sent it fleeing down into the murk.
Exploring farther along the left-hand side, the party turned up a pair of skeletons, two old Lydian gold coins, a sealed waterproof metal box, and a pair of magical spectacles, which Gizem put on to spare herself the hazard of direct eye contact, accepting the odd, elevated perspective they lent her. Jean-Zera drew the coins to hand with a Mage Hand, and they opened the box to find four small bottles, a diary, and a scroll, which Jean-Zera identified as a scroll of Greater Restoration; Sidra named two of the bottles topical anti-petrification potions, the other two remaining a mystery. Jean-Zera read out Petrus Gyllius's diary, and dark reading it made — of ancient waterworks and of stairs below the cistern, of Justinian dumping the bodies of magic-users beneath it, of a huge cage, of fellow lodge members, and of a dreaded she-devil. Soon after, the Black Queen Chess Piece they carried, with its serpent, began to vibrate near a great Medusa statue that faced the wall. Matching magic linked the piece to the statue: the stone serpent detached itself from the queen, slithered into a keyhole-like opening, and sprang an unlocking mechanism. The statue rotated to face outward, two nearby pillars crashed down and injured part of the group, the water began rapidly to drain, and a staircase stood revealed behind — as the Medusa, ceasing to be a mere carving, declared that none would free the snake demoness.
The fight was joined in the emptying dark. Miray took the shape of a crocodile and plunged back through the draining water toward the mirror, slipping past two Merrows that surfaced near her. The awakened Medusa loosed arrows from range, wounding Jean-Zera though missing Sidra; Gizem covered her eyes with her headscarf, shot the creature with her crossbow, and drew behind cover; Sidra scorched it with sacred flame and healed herself; and Jean-Zera summoned a swarm of secretary birds to harry its snake-hair and confound its gaze. One Merrow was caught by that gaze and turned to stone; the other overtook the crocodile-shaped Miray and mauled her until the beast-form broke, though by then the drained water ran shallow enough to keep her head above it, and she drove the Merrow off with discordant whispers and a parting strike. The Medusa climbed down from its platform and set upon Gizem at close quarters with sword and snake-hair; the blades missed, but the hair bit her and delivered a heavy dose of poison. It was Gizem who ended it, closing in to land a stunning strike that locked the creature in place long enough for the whole company to break away and flee down the new-found stairs.
Below lay a lower and much older prison complex, into which they descended, pausing at a T-junction of several doors to take a short rest — Jean-Zera attuning himself to the recovered drum and playing it while the others recovered and pored over Petrus's notes and the surrounding masonry, which they judged to date from Justinian's era. Investigating the nearest unbarred door, they found a storeroom holding a skeleton and a cursed keyring; keeping his distance by Mage Hand, Jean-Zera unlocked one cell safely, but when he tried the keys upon another the door burst outward in Greek fire, badly burning both himself and Miray and disclosing a screaming fire elemental within that cried for vengeance, retribution, and salvation, whereupon Jean-Zera shut and resecured the door and the two of them beat out the flames clinging to their persons. In another cell Gizem came upon a magical scroll painted with the fearful face of a man, which closer study showed to hold a person trapped within, one perhaps freed by a Greater Restoration or a Remove Curse; they left it in place and locked the room. In yet another, unbarred, they found the skeletons of an elven woman and a human man, a spellbook holding Disguise Self, Shield, Magic Missile, and Silent Image, a note, and two healing potions — the note and the surrounding evidence telling that the dead pair had been lovers out of Justinian's time, and that the man had been labouring at a spell to save the elf from an unnatural physiology.
The heart of the block was a massive central door, reinforced with chains and locks and metal spines and pictographic markings, and warded by the strongest anti-magic field in all that place, turned inward. Through viewing openings the company observed its several tenants. In one, a richly furnished cell laid with rugs and tables and drink, a young woman in a silk green dress lived at her ease and scarcely marked them — until Jean-Zera mentioned Osman, when she turned to ask whether Suleiman was ready for her, named herself Mahidevran Hatun, Suleiman's favourite concubine, and bore herself as though she had been secluded but a few days for her own safety. Through another opening a woman in a form-fitting red dress with a pearl pendant called herself the Shahmeran and asked whether they had come to fight or to free the prisoners. In a third cell Sidra glimpsed a turbaned, bearded, vizier-like man who flew into contemptuous rage at the very sight of her, calling her an unnatural creature sent to free him. And the last open chamber proved a torture room, full of rusted hooks and saws and pins and knives.
Returning to the woman in red, Jean-Zera asked her name and her wisdom. "The Shahmeran will suffice," she answered, and told them she had been imprisoned unjustly in a purge of the court under the reigning ruler's great-grandfather, her powers suppressed within these walls; she recalled, too, that Osman had visited her years before, had asked whether the party sought aid in avenging his killers, and had listened while they explained that they were labouring to decrypt his journal and to locate Mira. When they passed Osman's letter and journal-materials through the bars, she read them and declared that Osman had indeed set them to this task, named herself their ally, and asked whether they meant to keep her caged. Having weighed the risk, the company spent their labour prying apart the damaged cell door and freeing her — and the moment the door came away and the anti-magic field fell, the prisoner broke into manic laughter and revealed herself for what she truly was: a sorceress who had merely played along with their assumption that she was the Shahmeran.