This might be a bit of a crackpot theory, but I've been thinking about the Faceless Men and the religion of R’hllor. What if they were hired to execute the prophecies or support Melisandre's "magic" for example killing off Balon Greyjoy? Melisandre sorts Stannis out with a glowing sword, it's not something he went off and did by himself or by accident, so I don't think it's far fetched that they/Melisandre would be trying to make certain prophecies happen. I'm sure the religion of R'hllor has money, or maybe even more out there has converted one of the FM to their cause.
