Knights of Goldenhawk Tower
This citadel floats high in the Sky over the Sea of Swords of the coast of Amn near Athkatla. It is where arcane casters who were not members of the Cowled Wizards were sent to be imprisoned. It was garrisoned with Banite Fanatics, Cowled Wizards, and BaneClaw The Ebon Wing, a black dragon.
The Cowled Wizard’s Secret Library yielded the following Information:
During the spellplague many regions in Faerun experienced irregularities in the magical weave causing large chunks of earth to float into the air and hang suspended. These “earthmotes” as they are called can be as large as a mountain or as small as a fist full of earth. Three miles west of the city of Athkatla, high in the clouds, some 1,000 feet above the sea is a vast field of earthmotes known as “Crag Hang”. Inside one of the larger floating rocks has been carved the prison of Spellhold. A skychart with coordinates and bearings describes the secret location of Spellhold. Supplies and prisoners are brought to Spellhold via skyship. Only the cowled Wizard flagship “The Briar Rose” performs this task. Any other approaching skyships are attacked on site. Processing documents with hundreds of names list those who have been sent to Spellhold. Last on that list is Quagmire.
The Briar Rose is a huge skyship does not seem to regularly dock on land but rather is restocked with crew, supplies, and prisoners via other smaller skyships that are more commonly seen cruising above the skies of Athkatla by the city’s wealthy elite. Only the richest of the rich can afford such amazing flying ships. The installations and bases where the resupply comes from are much more heavily guarded than the Briar Rose itself. It seems the Cowled Wizards doubt the possibility of their flagship actually being attacked, but it is armed for battle. There are not any plans or maps of The Briar Rose but it is described in general detail. It has three decks. The main deck is the uppermost top deck which is open to the air. The ship is flown from here and is armed with 8 lesser and 4 greater ballista. These magical siege engines can reign down all manner of destruction such as fire, lighting, and freezing sleet upon enemy ships, castles, and armies. The other two decks are below decks inside the ship. The first is the crew deck which contains the living space of the crew – bedrooms, dining halls, work rooms, storage, etc. The bottommost deck is a large open air space encircled by a magical device called the Lighting Ring. The Lightning Ring is the heart of the ship which powers its ability to fly through the air. A lightning elemental is magically bound to the lightning ring. In order to pilot the ship, one must be trained in arcana and bend the lightning elemental to his or her will in what is called the taming ritual. The taming ritual takes at least an hour to complete. If one completes the taming ritual successfully, one masters the ship and can fly it by force of will by grasping the main ship’s wheel.
You do not find any schedules of supplying the Briar Rose. It does not seem like this is a common occurrence. It is a huge ship and carries a lot of supplies and living space for the crew. Even if you could somehow ascertain when the next supply ship was to meet with the Briar Rose, you might be waiting at least a week before it might happen.