The Causeway to Nowhere

Leading from the dwarven city of Santo in Tin Hou is a large paved causeway that mearly goes out into the ocean and stops by no ruins or towns. The causeway continues out into the sea and is somewhat visible for miles as continuing deep into the ocean.
Some rumour has it that it leads to a sunken city of treasures untold, others say it was created for giants to easily step out and wade without scratching their toes on rough corral. Even others say it was made by dragons as a colossal joke and demonstration of their power.
The truth is that is was once a trade route to an undersea trading city, but fell into disuse as the carts used for trade were disrupted during the great magic burnout a hundred years ago.
The city named Domhainsolas is at the end of the causeway and is carved out of huge basalt columns. Today it is home to a small number of sea elves, mermaids, and humans. Sustained by a magical artifact deep below the city that allows for terrestrial creatures to survive and breathe underwater. This artifact also provides power for the lights and some other magical effects.
One one side is the causeway at approximately 300 ft below sea level, and the other side a cliff leading to the deep port of Fallport a hundred and twenty feet below.
My band of adventures recently visited the city and found the artifact that provides breathable water for normal humanoids was a modified mystic engine that was attached to the only mage in the city and draining his life to stay active. They successfully repaired the device as the aging mage finally died. Leaving they hoped to be known by history as saving the town. But the final comments they overheard from the other leaders of the city was “We will find a good way to spin this.”
Using the city of Domhainsolas in your own campaign. The leaders of the city are the five holy maidens that assisted the mayor who was the mage that kept the city alive. They were conscripted as holy maidens to provide a good story and cement the ruling of the mayor. Originally the five holy maidens created the city as a shining example of civilization that could coexist between the deep world and the surface world. A hundred years ago when Grey’s family crashed in the sea and the engine was failing this genius youth found a way to keep the engine running by tying his life force to the engine, however not before a quarter of the humanoid population drowned. Grey’s lover, Vox, was saved by him turning to the necromantic arts, and she became a vampire. As he could not be further from the artifact that a few hundred feet, she became his mouthpiece and persuaded the city council to cede control to the young wizard. This was highly contested, but after recruiting four other maidens to establish a claim of divine providence, mirroring the city’s founding it was finally granted.
Over the ensuing years several replacements were made in the divine holy maiden’s. The ever dwindling population made this difficult and the current five are listed below. This group is no longer stable without the wizard alive, and was never particularly stable to begin with. (Spoilers for my players who don’t know all of this information)

Relations

Adversaries

Vox the vampire general of the city guard, who wears simple tight tunic and shorts and wields a sword with great efficacy. She personally recruited the remainder of the maidens, with an eye to having something over each of them so they always defer to her.
Arina an angel summoned, captured and forced by Vox to heal and sustain Grey’s life. Never comfortable with that she did however not want to doom half the city’s population to death if she did not. She still wears the flowing robes indicative of her order that can get in the way underwater and will wield a sickle if she must.
Winsk is the town hall guard captian, and suffers from a curse as a wereshark. She is loyal to Vox as she has never been prejudiced in the town since being granted the role of holy maiden and guard captain, and fears the reprisals of her actions if ever demoted. Always in a sleeveless military jacket allowing rapid transformation, she wields spiked chain and relishes close combat.
Dark skined Drea the sea elf, wears tight fitting clothes that allow for as much range of movement as possible and wields a trident. One of the few sons of servants in the city hall, he was extremenly loayal to Grey and agreed to dress the part of the fourth maiden to keep order. Idealist and now trapped by the charade, he is not sure what to do now that the engine is repaired.
Ala is the human spy and lurker of the group. An albino human who was persecuted as a child. Once adopted by Vox he agreed to play the part of the fifth maiden. Should such a secret be made known he fears to be run out of the city. Ala will use a knife and a medallion that allows him to cast charm person daily to get out of trouble if it presents.
Vox delights in getting people in tight situations and duplicities that will eventually lead to their destruction. Personally collecting the most misfit group of holy maidens that would still be sufficiently presentable to hold sway over the city. With one of the key lynchpins, the looming possibilty of death, finally removed and Grey having died, she must swifty establish control over the city so no traditionalist factions try to reestablish a city council not entirely in her control

Backdrops

Locations

The central city hall has several floors that are maintained by magic to be dry for visitors and diplomatic envoys. They have not been used much over the last century. In fact it has two separate libraries, the Dry Library and Wet Library. In addition, inside the city hall are the Vaults, White Sand conference hall, holy shrine of the 5 maidens and a shaft to the Mystic Engine.