The Ancient Peoples — a series by Les Lumens

Long before mankind came down from the trees, there were ancient, intelligent races living in the world. Though they are now known as monsters, and thought mere myths and legends, Lamias, Harpies, Nagas and the like are very real, and living in the shadows of a world dominated by mankind. Every so often, those worlds cross over. This series tells the tale of Aris, and his encounters with these ancient peoples.