Richter

You meet him in the same room he fought Dracula at the begining of the game at the top of the stairs that start in the castle keep. He is powerful with all his skills and moves (which you can also do when you play as him). Equip counter-holy equipment to hold him off and not get devastated against him. Hydro Storms are not refreshing for vampires. If you're one of those guys that likes a rush, meet him as early as possible and try to beat him without ANY holy equipment. It's pretty cool and really hard. If you beat Richter, you have a new problem: defeating gets you the bad ending. Go see Maria (at the room in the center of the castle, use the gold and siler ring together in the Clock Room). She will give you the holy glasses. You will be able to see a green ball above Richter's head. Attack that ball and free Richter and you will be able to access the Inverted Castle. Hitting the ball is not so simple since he moves around a lot, but it breaks easily.