The ruins do, in fact, seem to be from an ancient civilization; careful study of their layout, their designs, and more, seems to reveal that it was, in fact, either lizardmen or Yuan-ti; it's difficult to tell, but very clearly lizard-like, with an affinity for worshiping lizards and snakes. Many of the ruins, while no longer in use as a functioning society, still harbor treasures of a lost age... and the wicked inhabitants that guard them.