The Rise of Herk (Nnewts #2)

In this exciting sequel to Escape from the Lizzarks, Herk, the loveable Nnewt, is happy to have a new family and a new place to call home. But when the evil Lizzarks make an all-out assault on Amphibopolis using a giant monster, Herk must seek the help of the Megasloth to save the city and his adopted family. Meanwhile, Sissy, Herk's sister, discovers the dark truth about their long-lost brother Zerk.