From publisher blurb:
Adventure in the Island of Skulls!
Legend tells of an island hidden away from the rest of the world, where ancient creatures still walk the earth, and animals grow to incredible sizes unheard of elsewhere. This Island of Skulls, as it is known, is said to be home to the spearleg spider (CR 11) spider-like creatures that tower above the trees, horrible reptiles with skull-like heads known as skullslithers (CR 14), and most of all, a titanic ape known only as Kong (CR 30/MR10), said to serve as the island’s guardian and protector. This book presents game statistics for these three creatures, as well as game rules describing the massive magical storm that shields the island from outsiders.