How does Case compare Corto to the Tessier-Ashpools?

Case feels that Corto's insanity is something that he can understand. He sees where the man's madness comes from, and how events twisted him around until he broke. Case does not understand the madness of the Tessier-Ashpools. Ashpool was a mortal, human man whose power conflicted with his humanity and drove him to become something else entirely. The madness of the Tessier-Ashpools is much deeper, and more sinister than that of Corto.