“Do you know we have an entire room at our house dedicated to the Wonder That Is Him?”
Lord Cassius is Keefe's father, and part of the Sencen family. He worked for the council and is a powerful Empath. Lord Cassius's wife is Lady Gisela, who is the leader of the Neverseen. In Book 1: Keeper of the Lost Cities, he meets Sophie briefly on the staircase leading down from the Level Four wing at Foxfire, at the end of Midterms celebration. He took quite an interest in Sophie, hinting that he knew she was the mystery prodigy that Sir Tiergan was mentoring. Lord Cassius has proved to be very selfish and vain, even having a room filled with his accomplishments. He thinks Keefe should stop wasting his time and work harder in school. Lord Cassius wrote a book about Empathy, called The Heart of the Matter. Keefe, who had to read it inBook 4: Neverseen, described his father as a "torturer of innocent readers," but in later books, Keefe did say he learned a bit about the head and heart emotions. He is not a great father and has constantly belittled his son.
His name, Cassius means "empty", or "vain", referring to his character.
Lord Cassius is described as a taller man with many of Keefe's characteristics, but with blonde, slicked-back hair and neater attire.
Sophie meets Keefe and Lord Cassius in the Level 4 wing at Foxfire. She notices that Keefe is always down when his father is there. Lord Cassius calls Tiergan an "infamous mentor" when he (Tiergan) saves Sophie from sharing her identity as a telepath.
After Sophie's telepathy is revealed to the public, Keefe describes his father as very smug. Apparently, he had guessed that Sophie was Tiergan's prodigy, and Keefe says that his father always has to be right, and he always is.
During Book 3: Everblaze, Keefe believes Lord Cassius works for the Neverseen, but it is Lady Gisela who is working for the evil organization. Lord Cassius was completely blind to the fact that she was manipulating him.
In Nightfall, Lord Cassius tells Keefe and Sophie where Vespera hid her signature in Atlantis, proving he is somewhat worthy to be a part of the Black Swan, which he later joins. It was said earlier that Fitz had suspected Lord Cassius to have been the one to break his wife out of jail, which is something Keefe severely doubts, stating that his father cares more about his reputation than to rescue her.
- Lady Gisela (Wife/enemy)
Lady Gisela was Lord Cassius' wife. He confesses that he did feel love her, though those feelings were abandoned when Keefe, Sophie, Fitz, and Biana found her on Mount Everest with the Neverseen. He regards her as an enemy after her betrayal, and works with Sophie and Fitz to uncover his shattered memories in Legacy.
- Keefe (son)
Lord Cassius does not have a strong relationship with his son. He views Keefe as more of an object than his son, and constantly is thrusting unrealistic expectations on his shoulders. Often, he insults or scoffs at Keefe, since he was a small boy. From a young age, Keefe thought of Alden as a better father figure than Keefe. Later, he forced his son to live with him by threatening to withhold vital information that the Black Swan desperately needed. Throughout the last books, he starts to care about Keefe a little more, though Keefe stills is constantly annoyed by him, and doesn't take him seriously..
- Ro (son's bodyguard/nuisance)
Ro dislikes Lord Cassius immensely, and goes out of her way to make his life miserable, from feeding him terrible amoebas to insulting him every chance she gets. Lord Cassius generally regards her as an annoyance, though he tolerates her as Keefe's bodyguard.
- Sophie Foster (son's friend/forced acquaintance)
Sophie is generally hostile towards Lord Cassius, hating him for treating Keefe so terribly. She hates that he is part of the Black Swan, and originally believed he was the traitor to the Neverseen in Keefe's family. However, Lord Cassius, on the other hand, has grudging respect in Sophie, though he is very cold towards her. He allows her to search his memories, and has faith in her abilities, though he probably wants to utilize them for himself.