Moss Giant Island is a small island located west of Brimhaven. The island has five moss giants, and requires 10 Agility (Ropeswing) to access it. The island offers very good safespots to kill moss giants. Beware of the Poison Scorpions when making your way to the island.
You can safespot the moss giants by using the south shore and middle between the trees north of the island.