Dassuk was one of the Monoids' slaves aboard the Ark in the 57th Segment of Time. He and the other slaves were familiar with the First Doctor's role in their history. Dassuk was one of the many slaves who mistrusted the collaborator Maharis.
Dassuk and Steven Taylor attempted to kidnap a Monoid but were forced to let him go when another Monoid killed one of the human slaves.
After the Monoids left the ship, Dassuk helped to search for the bomb that had been planted by the Monoids. When the group found a launcher on the ship, Dassuk and Maharis took it to Refusis II to contact the Doctor.