Lotion Soronnar wrote...
Which begs the question how did Merril learn anything then.
Not really. Gaider's said that once she went to Kirkwall, she studied what scraps of lore she could find on the Eluvians and extrapolated information from them, applying it to the shard of the mirror she had.
All of Merrill's work after cleansing the shard of the Taint was based on what research she could find. She never relied on the Demon to help her aside from learning blood magic, as Act 3 has her trying to reestablish contact with him -- something that fails, due to both the Demon's ability to communicate being directly tied to proximity, which the short story tells us, and
possibly Marethari having already freed him at this point.
Also, Metharari wanting nothing to do with them doesn't mean she knows nothing about them... In fact, her strong opposition to it could indicate that she indeed knows a lot more than she is willing to admitt.
She said she knew nothing about them in DAO, and when Merrill went to her asking Marethari to combine her healing magic that could combat the Taint in its unamplified form (per Origins) with Merrill's -- as she was taught it by Marethari -- Marethari refused. And this was not long after they fled Ferelden, where Marethari said "I've never heard of any such thing in all of the lore we possess".
Which was what forced Merrill to use blood magic, as she only had one viable alternative: Teaming up with her Keeper. Lyrium would've also worked, had she been able to get some without serious ramifications to her or her clan. But she couldn't, so blood magic was the last option available.
Further in the game, she says she wouldn't study them, work on them, or do anything with them at all.
And she doesn't bother to really inform Merrill of anything in the ensuing years other then "It's EVUL!!!!", which isn't going to do much to dissuade a person from a certain path. Specifics would help when you're dealing with something from an ancient culture you know little about.
Given that she comes up with her "revelation" in a moment where she's possessed by a Demon -- who as we find out can perfectly mimic Marethari -- and made no effort to tell Merrill about this revelation in
any of the seven years Merrill was working on it, I'm inclined to believe that she didn't do the research at all.
Which is supported, in all the time we see her, by her unwillingness to research them.
She says in Origins she knows nothing about them, and in DAII that she wants nothing to do with them and that she wouldn't study them anyway (in Act 2, IIRC).