An old iceburg on Hook Mountain begins to melt, and encased in it is an ancient being known as the Ice King. He begins to destory Snow-Man's caslte at the top of Hook Mountain, and frezzes Snow man in solid ice. Snow-Meow, his faithful compainion seeks out Lion-O to do away with the being and save his master. Lion-O fails, and is also frozen. Once again Snow-Meow sets out to find the other Thundercats. They arrive only to face defeat, and Cheetarah is the only one to survive. She uses the sword to restore Lion-O to normal, and he in turn restores everyone else. They discover that the Ice King is looking for an ancient egg to see his wife, the Queen one last time before he dies. They understand his madness and assist him in finding the egg (thetvdb.com)