Malatius and Grock is a company which hires Geralt to travel on their barges in the Pontar Delta between Foam and Novigrad because they have been losing cargo and men to a mysterious monster. Six of Geralt's trips are completely without incident, the same cannot be said for the seventh.
The Malatius and Grock Company is mentioned in the novel "Blood of Elves" ("Krew elfów").