Moonshadow

Stories about the world of the gods are sparse, and the gods themselves give away little. Some believe that the gods were born into a world where they had to discover everything themselves, with help hard to come by and then only for those who could withstand the rigors of speaking with spirits; and it is known by all that the gods created this world and populated it a little over ten thousand years ago, teaching those early humans the rudiments of farming, artifice, magic, and more. Dwarves were taught even more lessons, and skyships appeared within the first five centuries of life on Kytheria. The first voidship, however, was built by elves.
Moonshadow preceded every other voidship by millennia, for her owner kept it and its workings a secret. The outer hull is crafted entirely from ebony and orichalcum with the same vaguely crustacean shape used by almost every voidship since, and when its owner neared death she finally let others know the secrets of its construction and also of the vast cosmological charts she'd made in her centuries of voyaging. The charts themselves are nearly as precious as the ship, which disappeared four thousand years ago.
Moonshadow was unique in many ways, and one of the most crucial was its ability to navigate beyond the Girdle. No voidship made since has been able to duplicate the original navigation system perfectly and the scattered worlds beyond the Girdle remain a mystery as a result. The ship likely has these charts recorded within its crystalline memory core, and is also capable of discerning and using the navigation markers set down by the creator in her travels, and its this level of sophistication that others can't seem to achieve. Even if someone could find the Moonshadow it's unlikely that voidship construction would benefit, though the finder could explore relatively untouched frontiers.