Tibalt's mostly running around in the backwoods, but I think there's potential to flesh him out if you give him an interest in the human body's response to pain. Like, give him a little band with a healer, an Avacynian priest who's been branded as a heretic by the Church for brainwashing townsfolk, and children, in the outlying settlements ravaged by the plague of monsters from our first trip to Innistrad. So he's been convincing the children to take up arms against the cathars because he believes that they're being controlled by demonic forces. Finish it off with this priest confirming his beliefs with stories he heard about heroes pure of heart from his mom when they were on the run, fleeing vampires or something.
In order to get the maximum yield from his studies, Tibalt has some devils stitch up a cloak of skins - the cured skins of people brainwashed and/or brutalized by the priest. He then decks the priest out in this macabre motley before each experiment.
Anyway, so when Tibalt and his little band are prowling around, they send in the priest. Before the priest reaches whatever town or farm, the healer is sent in beforehand. When the priest shows up, the healer calls him out for his crimes. The enraged townsfolk go to beating on him. Then another of Tibalt's band that can pick the townsfolks' minds tells Tibalt exactly what's going on upstairs when the townfolk are stimulated by the accusations of abuse hurled at the priest in their band. Some of it comes from the priest as well - Tibalt lets them beat the priest bloody, then sends him some devils to save the whimpering sack of soiled faith.
And so the priest is mostly kept as something of a prisoner, continually stripped down mentally and physically before being restored by the group's healer. To endure more of the same because of Tibalt's interests in how pain actually functions within the human body.