Complex sentence: The Goblin King is revealed to be Willow's father as he punishes her for the trouble she caused and her selfishness by having her grounded for one year but then admits that he's relieved to have her back.
Split into simpler sentences: The Goblin King is revealed to be Willow's father as he punishes her for the trouble she caused by grounding her for a year. Yet the Goblin King admits that he's relieved to have her back.