What’s up with Jaqen H’ghar and the Faceless Men?

Jaqen H’ghar is probably the most confusing Game of Thrones character. Who is Jaqen? What’s his relationship with Arya? Is Jaqen Syrio Forel? Who’s the “alchemist” at Oldtown, and what does he want? What do the Faceless Men have to do with Valyria? Were the Faceless Men involved in the death of Balon Greyjoy? Could they be working with Euron Greyjoy to orchestrate a huge terrible blood sacrifice? This video contains spoilers for Season 6 of Game of Thrones, and Books 1-5 of ASOIAF, and a TWOW sample chapte