I still get the impression that was Myrkul's doing via Balthazar.
Though, this leaves the bizarre notion of Balthazar, with the power of Myrkul... Somehow managed to not only pass all of Shar's trials, but also enter Shadowfall and use magic to bind Aylin to Ketheric all without Shar herself noticing or doing literally anything about such a tresspass.
I suppose Shar's pretty lenient of who goes through her stuff... Given that we can be literal Selunites and still reach Aylin in Shadowfell and she only cares if Shadowheart disobeys her... Though that just seems like a poorly formed handwave over a significant plothole because of the nature of sticking Aylin at the end of the Shar temple despite it making absolutely no sense whatsoever...