Tverdoruk was a soldier loyal to Prince Egmund of Kerack and served under Captain Ropp. During the wedding of King Belohun and Ildiko Breckl, Ropp was to supposedly act as a point of contact and support for Geralt should Xander have tried to orchestrate a coup in an attempt to usurp the throne of Kerack. In reality, Egmund had plans of his own and meant to blackmail Geralt into acting as his assassin. To this end, Tverdoruk and his comrades Richter and Samsa kidnapped and held Dandelion under threat of death if Geralt refused to comply. Tverdoruk was to lie in wait alongside Richter at a secret exit that Belohun would have been brought through, and would have assassinated the king there.
The witcher responded by killing Tverdoruk and his two compatriots and incapacitating the captain, hitting him so hard he was left with shards of nasal bones in the brain.