Jeb performs a ceremony over four graves of men who have recently died, one of whom is Thomas. The incantation to the god of the underworld is to "open the door of a thrall to send out those that can be his hands that are not his, bodies without minds and hearts that do not beat." They rise from the dead, ready to serve the Leviathan cause. (962)
In his undead form, Thomas was responsible, along with his three comrades, for kidnapping Julia Hoffman (963), and burying Quentin Collins alive (964). As a result of the Leviathan Altar being destroyed, the zombies were reduced to skeletons (966).