Cool theory. One nit to pick--I dont think Mavra attacked Harry and Thomas for no reason. I think she was gunning for *Thomas*. During the first attack Harry hadnt even been officially hired. Then at the party, when she learns of the attack, Justine says something like, 'I thought you didnt have to worry about Mavra'. Then, during the attack outside the movie studio, the MavraPuppet talks about Thomas as 'the one who betrayed us.' I think your idea she was out to get Harry here is incorrect, but its really a side note to a really interesting theory. And I keep finding a bunch of Round Table references lately as I'm rereading the books...its kinda funny, if you're right, that Morgana/Mavra traded her own knife to the Leanansidhe/Lady of the Lake. Didnt excalibur come from her? So they swapped their own weapons?