Will Batman’s great immortal enemy be the major villain on The CW’s Arrow? Episode 5 of Season Two is called The Demon’s Head according to GreenArrow.net and “will feature a character called Awwal who is a Dark Archer, trained by Merlyn. He is after Lisa.”
The Demon’s Head is the translation of Ra’s Al Ghul, leader of the League of Assassins in Batman mythology. Liam Neeson played Ra’s Al Ghul in The Dark Knight Trilogy but there were no demonic references.
Ra’s returned to Batman comics at the end of Batman, Incorporated finale and in September’s Villains Month issue of Batman and Robin.
Here’s a link to Arrow Season One which featured Merlyn, Deathstroke, China White and Huntress.