This title is a phrase in the fictional language of High Valyrian. It is spoken in the episode by Jaqen H'ghar who, after Arya refuses to go with him to Braavos, gives her an iron coin and tells her that if she ever wants to find him again she should hand the coin to anyone from Braavos and speak the words "Valar Morghulis", and they will take her to him. Valar Morghulis translates to "All Men Must Die" and is a traditional motto in Essos, the land mass to the East of Westeros. It is meant as a reminder that death is unavoidable, similar to the latin phrase "memento mori". It is customary in Essos to respond to the saying with "Valar Dohaeris", meaning "All men must serve".
