The Quest for Truth

Hidden mission. After defeating Sar-I-don't-remember-the-name, it doesn't return you to the spirit world. The mission is completed, and you're taken to the menu. It's impossible to finish the campaign. I hope they aren't interconnected, and I can load from a save without significant losses. Also, it's not entirely clear why there's a Sylvan tree that reaches the ceiling, and you run into it before you finish off all the enemies (although there was growth, but not immediately, and the second level only appeared somewhere near the end).