In the first episode of Legends of Tomorrow, Rip Hunter mentions three despots: Caesar, Hitler, and Per Degaton. I haven't watched Arrow, but I do watch The Flash and Supergirl. The mention of someone who hasn't appeared yet strikes me as unusual - unlike the MCU, DC's adaptations seem positively loath to mention anyone who's not directly involved in the adaptation's plot. Per Degaton, Wikipedia tells me, is a time-travelling supervillain.
Is Per Degaton slated to appear in Legends of Tomorrow, or in Arrow, or in The Flash, or has he appeared already?
A young Per Degaton does appear in episode 10, Progeny. And, it seems, in Legends of Tomorrow, Per Degaton is just a patsy for Vandal Savage, wiping out much of the world's population, thus preparing the world for conquest by Savage.