It terrorizes the Ceratogaulus society living in the underground cavern Spike falls into. When they ask Spike (believing him to be the "Big Wise One" of their folklore) to defeat it, Spike is afraid at first, until he sees that the Great Hideous Beast is about a tenth of his own size. He easily imprisons it in a heap of fallen rocks, but the Great Hideous Beast escapes when the other main characters lower a rope of vines down to help Spike get out. While Spike takes a different path back to ground level, the Great Hideous Beast grabs the vines, surprising the others when it is pulled up. When it sees Spike aboveground, it takes off, tripping over the vines, then gets up and runs away, with the vines still wrapped around its ankle.