The Faceless Men are a guild of assassins who regard death as a gift and stoically grant it to any and all. But other than their odd religion and their penchant for killing, very little is actually confirmed about them.
This has led to wide speculation about who they are and what there goals might be. The following is a brief description of some popular theories regarding the Faceless Men and their activities.
This article does contain spoilers for both the show and the novels.
Faceless Men brought about the Doom
As legend has it, the Faceless Men were founded by Valyrian slaves whose lives were so miserable that they longed for the mercy of death. This mercy, or “gift” was dutifully carried out by a slave who took pity on his peers, hearing them cry out to their various gods. He eventually concluded that these were not separate gods at all but one god with many faces. Though the first kills were slaves, the gift was eventually passed on to the masters.
However, the details of how exactly the masters were slain are not provided. Which does raise questions considering how many masters there were, and whether the Faceless Men attempted to simply give them the gift all at once: through the Doom of Valyria. It is theorized that this was accomplished with dragon eggs, which many believe to be quite volatile and dangerous.
Balon Greyjoy was killed by a Faceless Man
The third novel in the series, A Storm of Swords, contains a very revealing excerpt:
“I dreamt of a man without a face, waiting on a bridge that swayed and swung. On his shoulder perched a drowned crow with seaweed hanging from his wings.”
Balon Greyjoy died crossing the bridge of Pyke. Quite conveniently, his brother Euron (nicknamed the Crow’s Eye) returned from exile soon after. And within a short time, he rose to become the new King of the Iron Islands. Seeing as the show has not explicitly mentioned Balon Greyjoy’s death yet, he is presumably still alive, which may mean we actually get to witness a Faceless Man at work. Jaqen’s return as a character may offer just such an opportunity.
Euron has also mentioned that he used to own a dragon egg, which if the previous theory is true, would be a very appropriate payment to the Faceless Men.
The Many-Faced God is the Other
Some have speculated that the Many-Faced God is in fact the Other, which the Red Priests regard as the great evil. If this is true, the Faceless Men are working directly against R’hllor and aim to bring about the apocalypse rather than end it. This has led to speculation that they actually intend to breach the Wall and let the White Walkers pour through.
Their belief that life is suffering and death is mercy, is quite compatible with a longterm goal of humanity’s extinction. Which they would view as salvation rather than doom.
Varys is a Faceless Man
Given his penchant for disguises, intrigue, and slippery motives, it is not hard to imagine Varys having connections with the Faceless Men. Approaches to this theory vary, some believe Varys was killed by a Faceless Man, who now assumes his form, others believe he was one of them all along, while still others believe that he is employed by them, but not a member himself.
His unseemly talent for gathering information through spies does seem to hint at him being a part of a larger organization, but whether or not that organization is the Faceless Men can be debated.