Scientific name -- Homo Saipens (deceased)
Size -- 5-6 ft tall
Diet -- Eats the flesh of it's enemies

Many cultures around the world have their own takes on the concept of bodies returning to life to wreak havok upon the living, the Greeks were no exception to this, and believed the bodies of the deceased could be brought back to like with Katadesmoi, essentially a Curse Tablet shaped like a leaf, made of lead. The releatives of the deceased would place these tablets upon the dead's graves if they believed their dead were killed wrongly, essentially the precursor to the French Revenants.

These Wraiths are corpses of long ancient people brought back to life by Charon, who has been cleared by Hades to protect his interests, and fight against the forces and fanatics of Kronos who have been wrecking havok upon the Olympian gods' followers. It would only be natural that these once mighty warriors who successfully warded off the Atlanteans thousands of years ago would rise again to fight the Titan followers.