"The Demon's Head", Ra's al Ghul is an actual comic book character. He made his comic debut in June 1971 in Batman #232. He is known as the leader of the League of Assassins and for virtual immortality by submerging himself in mystical Lazarus pits.
Whilst searching for Merlyn the team go looking for Master Jansen in a Buddhist monastery. In the Green Arrow comics Master Jansen is the friend and teacher of Connor Hawke, Oliver Queen's son and the second Green Arrow.
In a flashback Oliver refers to a Ferris Air flight. Ferris Air is owned by Carl Ferris. Father of Carol Ferris girlfriend of Hal Jordan/Green Lantern in the comic books and also means that they exist in the same universe.
This is the first episode in season 3 that has 'The Dark Archer' theme soundtrack. The last one was in Unthinkable (2014).
The proper pronunciation of Ra's al Ghul is actually Reysh al Gool not Raz.