I kinda suspect Shadowheart's
voluntarily repressed memories are her being a Selunite that got brainwashed into thinking she's a Sharite
. I've also heard that she might be
the character from The Unclaimed book in the dusty tomb where the talkative skeleton is
.
If you read all the books you find carefully, and put them together, particularly those in the Apothecary, Nevromancer Lair and Spider Lair, this is basically the story:
In 1371, Moonhaven was a quaint village who worshipped Selune. Ilyn Toth, the Necromancer, came with his apprentice Eliette and set up as a doctor to hide from the Zulkiers. They were kidnapping people from the village, most likely children since the poster implies children being kidnapped and vanishing and Ilyn Toth said his familiar was helping him kidnap people.
But the Dark Justiciars targeted Moonhaven and the Druid's Grove because of Selune, and perhaps something else since the Grove seems quite special. Harpers and Druids united to fight against the Dark Justiciars, but they were betrayed by one of their own, Ketheric. Roa was a druid who joined the grove to help fight the Justiciars. Halsin was there as well, as implied by his entry in the last volume of a series of 4 books about this. Moonhaven was destroyed in 1371 when the Justiciars invaded. Ilyn Toth was killed by them but Eliette was taken by Drow to the Underdark where she went insane in their captivity and became obsessed with Lolth and arachnomancy.
Halsin, Roa and the Druid/Harper alliance fought back against the Justiciars and pushed them back, probably to Moonrise Towers where there was a final fight. Roa died, but Halsin returned to lead the grove.
There was definitely some connection to Shadowheart, so some theories about her being from Moonhaven and a Selunite make sense. I think either she willingly betrayed her people as well, and that she is Shar's Chosen in the Unclaimed book. Her memories were wiped so she wouldn't remember her betrayal and would continue to serve Shar instead of allowing guilt to turn her back to Selune. My theory is also that she died during the fight at Moonrise, and she went to Kelemvore who had pity on her and maybe resurrected her back to Faerun to redeem herself, now 100+ years later.
In order to redeem herself, she thinks she has to do something more for Shar, and so she's being used again, used to steal the Gith weapon so Shar can use it for her own dark purposes.
I don't know for sure, of course, but that's my theory anyway.
