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This article contains plot details from the latest books.
Forgotten Secrets are memories so dangerous that Councillors have to purge them from their minds and store them in caches. Until a secret document was given to Sophie by Lady Gisela, Vespera was part of a Forgotten Secret. Consequently, only the guards that tended to her in prison in Lumenaria knew of her existence and who she was. There are about 50 Forgotten Secrets.