In Finn Family Moomintroll, Hemulen steals their barometer, and this causes them to relentlessly pursue him until they get it back.
The Exploits of Moominpappa - Here, several characters refer to the Groke eating people: the Joxter claims to have a cousin who was eaten by the Groke, and the young Moominpappa saves the Hemulen's Aunt from being eaten by the Groke.