Right, Uncle Deckard was a Horadrim which are basically an organization of powerful mages and wizards who were dedicated to finding a way to stop powerful demonic forces. Which meant collecting old stories, histories, accounts from various things in less then friendly places. Uncle Deckard's focus was on the Prophecy of The End of Days, and how to circumvent it if such a thing was possible.
Old skeletons sometimes walk again, especially if enough magical power, or demonic, rests nearby.