Lask Frildur was a large male monitor lizard of the island Sampetra. His species was indigenous to the tropical isle but had been employed by Ublaz Mad Eyes, the pine marten emperor of the island, as his shock troops. Lask was the head Monitor General and Ublaz's strong right claw. He had pebbly grey-blue skin which turned green when he was ill. Like most monitors, he spoke in a sibilant voice that emphasized his "S"s and "Z"s.
He was sent by Ublaz, along with a score of his best monitor lizards, across the western sea on the Waveworm with Romsca's crew to fetch the Tears of all Oceans from Redwall Abbey. Failing to locate the pearls, he instead took Abbot Durral as a captive to bring back to Sampetra. He was followed by Martin II, Clecky, Grath Longfletch, Plogg and Welko. Aboard the Waveworm on the return journey, he was at constant odds with the ferret captain Romsca, who treated him and his followers as inexperienced landlubbers (which they were). Hunger and lack of meat eventually caused his sanity to begin to ebb; finally, he and Romsca fought and slew each other. Lask's successor as lead lizard was Zurgat.