The Flash is a show thats dabbled in time travel and alternate Earths but the idea of immortal madmen and reincarnating Egyptians is new even for this show. Typically, The Flash explains away these more incredible phenomena through their relation to the realm of science, but that doesnt seem likely to be the case here. The Legends Of Tomorrow trailer depicted scenes set in Ancient Egypt and Kendra even got a few flashes of that setting herself. This suggests that sooner rather than later, the show is going to explain just how its possible that Hawkman and Hawkgirl have died 206 times. The obvious explanation could be the aforementioned story with Hath-Set and the cursed dagger, but it seems like with a show as bombastic as The Flash that that explanation wont cut it. Something truly magical is going on here and hopefully it wont require waiting until the spinoff to find out just how it's happening.