The first question Damian asked himself as he appeared inside the Forge, with Claire and her sister in tow, was — did he trust Little Faerie? The logical answer would be no. After all, he had only known Little Faerie for just a few hours.
But then, why was he so certain Little Faerie wouldn't take Claire's or Raven's Pure Innate Souls for herself? It was due to two reasons.
First, if the information his mother sent him was correct, then Pure Innate Souls couldn't be stolen. There was a clear line between Innate Souls and Pure Innate Souls. You could either be born with an Innate Soul or you could artificially make one for yourself. However, for Pure Innate Souls, you could only be born with it.
It was for this reason Claire and Raven had been sealed in the first place. Whoever had done this had clearly sensed the Pure Innate Souls in them, but unable to rip it away from them, he decided to seal them.
