This is an interesting theory, which may be utterly destroyed by the recent events in the television show that showed that Missandei and Grey Worm may be entering into a romantic liaison. Until now it was suggested that she might in fact be a Faceless Man as she seems wise far beyond her years. In the books shes meant to be only around eleven years old (as specifically stated in A Dance of Dragons). There are several clues to her unusual nature, which includes her ability to sneak up on Ser Barristan and her ability to hear noises from half a mile away. She was meant to have a brother who was killed in Astapor, but that simply could have been another Faceless Man as who is to say that all of them are as technically proficient as Jaqen Hghar. Missandei also seems to fall into a nasty habit of referring to herself as this one, but not on a constant basis, and she is often found reading old scrolls from the Meereen library. While this might be a red herring, it could be that the Faceless Men are searching for information on something and they have been secretly guiding Daenerys into taking Meereen to gain unhindered access to their libraries.
