Going back to the discussion about Melisandre and the Red God from a few pages back...So far we've seen or heard of Lord of Light followers demonstrate:
-Immunity to poison
-Resistance to the cold
-Ability to birth demons
-Ability to resurrect multiple times
-Seeing the future
-Igniting swords with their blood
-Ability to converse with fire voices
-Blood curses**
**People scoff at this one, claiming the events were set in motion long before Melisandre performed the ritual with the leeches, which is true, they were. But that's sorta how curses work , right? The accursed don't spontaneously combust or instantly drop dead without reason, rather cause & effect play out in ways that ensure they're met with tragedy and misfortune. How many schemes and missions fail horribly in this story? Isn't it a bit odd that arguably two of the most complicated and intricate plots we've seen worked flawlessly given all the ways they could have, and probably should have gone wrong? Nevermind the timing.
To be fair, it's also possible that Meli was able to discern the deaths of the usurper kings from the flames and used the whole blood ritual to manipulate Stannis. This would fit with how she admitted to sometimes using smoke & mirrors as a way to lead people to the Lord's truth. Were it merely just some trick, though, I'm not sure why she would go through the trouble of tracking down Gendry in the war torn Riverlands when any ole Low Born pleb would have sufficed. It also doesn't explain why she threw in Balon, who's 'death' was a bit more abstract. Besides, would she really waste precious King's Blood on a scam?
What happens in the wake of this most recent offering of King's Blood will definitely be telling. I'm inclined to believe both her and the Lord of Light are legit at this point. Despite all the hatred and distrust Melisandre garners from fans, it's hard to point to anything she's claimed or predicted that's been inaccurate. Certainly Stannis has no reason to doubt her; everything he's gotten thus far is directly because of her.