Theodore and his fraternal twin sister, Katie, were born evil. Little else can explain the twisted relationship that they developed so early in their childhood or their utter lack of conscience, despite the perfectly normal childhood they shared. The incestuous pair arranged an accident for their parents when they were barely thirteen and then manipulated their foster parents until, in the midst of the mental breakdown of their foster mother, they struck out on their own. Both were just past their majority when they were arrested in connection with the murder of a man who had allegedly tried to rape Katie (in truth, she was seducing him in order to rob him and her brother, in a fit of temper, struck the deadly blow) and that is when Martin LaSalle involved himself, using his connections to get the charges dismissed and the twins released into his custody.
The reason for his interest was the shared mystical talent that the two shared. Not only did they exhibit strong indications of telepathy between them, but Katie was an actual spiritual medium, a gift which she occasionally used for money and which is what drew LaSalle's initial attention. Testing them, he discovered that both had far more talent than he'd hoped and he Embraced them both so that they might become apprentices. Unbeknownst to him, however, the two inadvertantly Blood Bonded each other before he was able to and so have no particular loyalty to their sire, other than the fact that he is currently useful as a mentor and money source.
Theodore is more outgoing than his sister, if by outgoing you mean brutal, violent, and short-tempered. Athletic and direct, he is really little more than a thug in both demeanor and mindset. His studies have been in keeping with this, focusing on the destructive and the useful for one accustomed to violence. He's progressed almost as quickly as his sister, though his talent is more intuitive than hers, so it seems likely that she will continue to outstrip him as time goes on. Much of his 'study' also tends to focus on unnecessary and brutal experiments which his sister encourages and which cause his sire to seriously worry about the mental health of the two.
He is happy at the chantry, insofar as it is safe, he has the run of it, and he can come and go as he pleases. Similarly, he'll put up with Martin and his posturing so long as he continues to pick up the meal ticket and provide the texts he needs to study. However, he is aware of Katie's plans to eventually move on and fully supports her, regardless of his own lack of discontent. He rationalizes this by noting that his own studies aren't going to get much further under Martin, to the extent that he needs to rationalize anything where it regards his sister (which is to say, not much at all).
Of note is that of the two apprentices that have disappeared since the 1970 raid, only one was actually a casaulty of Sabbat terrorism. The other was killed by Theodore in a fit of anger when he caught him spying on his sister. He disposed of the body in the bayou near Lafayatte and hoped it would be assumed to be the revenants' fault, which it was. However, should any suspicion be raised in Martin's mind, Theodore is well aware that he could easily pick the details from his mind and isn't anxious to discover what punishment his sire would see fit to impose, should this occur.
Theodore is more sociopath than psychopath, and thus lacks his sister's tendency to be easily bored and isn't quite so devoid of emotions as she. He does, however, suffer from an almost complete lack of ethics and has extremely poor impulse control. He tends to get violent when angered and is angered easily. He also has a juvenile disrepect for authority and goes out of his way to pick fights with authority figures (including Martin, though the regent has learned to ignore him). He is generally abrasive, brooding, and irritable and most of the residents and visitors of the chantry avoid him.
Theodore is obsessed with his incestuous relationship with his sister and is fiercely protective of her, in the wholly irrational, paranoid, homocidal way only a sociopath can manage. He has almost destroyed more than one apprentice in the chantry who has in some way cross his sister or even looked at her the wrong way, and most visitors to the chantry know enough to leave them both well enough alone. Given her tendency to use seduction as a tool to manipulate people, he has ended up foiling her plans on several occasions when petty jealousy got the better of him. She has berated him constantly for this behavior and now tends to leave out details when telling him about how she got blackmail material when she fills him in.
His dislike of authority translates to generally poor relations with Martin, who only suffers him because of his talent and that of his sister, whom he is sure would leave (or worse) if he harmed him or sent him away. Thus, the two have a tense relationship where they tend to avoid one another except when it is absolutely necessary. As for the third apprentice, he has a mixture of lust and distaste for her that has led him to be alternatively cruel and kind to her, such that she now refuses to deal with him at all, a fact which pisses him off and may end up leading to some sort of assault.
He also dislikes Julia Kirchner, mostly because she was the favored childe before she moved to Shreveport, but has a grudging respect for her childe, James, for defecting to the other side (a possibility which has crossed his own mind on occasion, when Martin has him pissed). He is smugly happy that she's currently in disfavor because of this event and has lost her chance to rule Shreveport.
He cares very little for the other kindred in the area, only really mustering emotions for the Lafayette broods, whom he hates because their attacks on the chantry have endangered his sister. Harrying them has been the main thrust of his cooperation with Martin and the plans of Baton Rouge and he was one of those who took part in the 1970 raid which almost wiped them out.