The actor (Casper Crump) is Danish, and judging from behind-the-scenes videos, he's using his natural Danish accent in the role. I have no ear for accents, so I couldn't really trace it until I looked it up, but I think it fits the character very well to have an exotic, perhaps hard-to-discern accent. The Hawks reincarnate, so they would have accents based on their present lives, but Vandal has lived through the millenia, picking up hundreds of languages in order to consolidate his power base. It makes little sense for him to have the same accent in his first life (as Hath-Set), but I could see him settling down on a particular way of speaking English and sticking with it for hundreds of years.
Maybe his public backstory for Curtis Knox (and other aliases) had him being born and raised in another country and coming to the United States at college age.
