Quintessence — David Walton

Imagine an Age of Exploration full of alchemy, human dissection, sea monsters, betrayal, torture, religious controversy, and magic. In Europe, the magic is thin, but at the edge of the world, where the stars reach down close to the Earth, wonders abound. This drives the bravest explorers to the alluring Western Ocean. Christopher Sinclair is an alchemist who cares only about one thing: quintessence, a substance he believes will grant magical powers and immortality. And he has a ship.