ThunderCats 1985 Season 4 Episode 20 The Book of Omens Episode Title:The Book of Omens.Episode Description:Finally, Panthro deciphers how to use the Key of Omens. He enters the code to open the lock and the Guardian of Omens is suddenly summoned. It tells the ThunderCats they have twenty-four hours to present both the Key and four other items to the four places in disgrace – i.e., plagued by geological disasters – all over New Thundera. Everything was proceeding correctly except for the Key, which Mumm-Ra stole. However, Mumm-Ra enters the Book of Omens just when Lion-O finds him, and they battle inside the Book. This presented a satisfying finale for the complete series, albeit one with an open ending.