The second season of Arrow has incorporated even more DC characters than the first. At the start of the year a returning Malcolm Merlyn, last season's Big Bad, name-dropped Ra's al-Ghul, traditionally one of Batman's greatest foes. Since then we've seen the League of Assassins come to Starling City. Ra's al Ghul's 'other' daughter, Nyssa, also made a recent appearance. Clearly Arrow is going to be facing the Demon's Head in the not-too-distant future, probably next season, once he's dealt with Deathstroke. Most people know Ra's al-Ghul from Batman Begins. In Christopher Nolan's version, he was combined with the mercenary Henri Ducard to create a more realistic character, one who merely used the name as a cover. Arrow season one would have copied this idea, given its borrowing from Nolan's trilogy and the fact that it strived to be realistic. But season two has seen a radical shift in the Arrow universe, in which the comic-book version of Ra's as an immortal warrior king is more palatable. The mysterious Mirakuru, a key plot point in season two, bears strong resemblance to Ra's Lazurus Pit. So ex-mercenary, eco-terrorist or ninja-cult leader, the following are five actors that could play different interpretations of the iconic character.