If Seth were to say that he had a very bad and tough time while staying at the Demonic Shadow Royal Clan castle, ninety percent of it, was due to First Shadow's influences. Velgor was always a fear inducing presence for him, a person that was mysterious and shrewd. But if Velgor was the true definition of terror, First Shadow was the true horror.
Velgor was the one who ordered and First Shadow the one who executed. All the hardships and tortuous trainings Seth had to pass through, were always commanded by First Shadow. That woman was nothing good and she had a thoroughly twisted personality; at least that was how Seth had always seen her, as an executioner that would mercilessly butcher anyone for her master.