http://www.ign.com/articles/2015/12/03/arrow-legends-of-yesterday-review
Okay now that part 2 of the Arrow/Flash crossover event is over, let's see who the villain really is.
Seems DC has an abundant of immortals going around, Ra's Al Ghul, the Sensei, Hath-Set and Vandal Savage to name a few.
The Flash/Arrowverse has introduced us to their version of Vandal Savage. Funny how the TV or any other version of a comic book character becomes something else but somehow it makes sense. Well Vandal Savage turns out to be Hath Set, the Egyptian high priest who kills Prince Khufu and Chay-Ara. Orignally written in the 1940's by Gardner Fox and later on enhance by writers William Messner-Leobs, James Robinson, David Goyer and Geoff Johns. The writers of the Arrowverse then somehow connects all the dots and made Hath-Set and Vandal the same person.