I need to power three crystals to release
Head down the stairs to the North. When you reach the base of them, look to the left. You will find the Crystal Emitter. Head over to it and interact with it. This is one of the two crystal emitters in the room holding the King.
Scattered throughout the room are Crystal Prisms. You need to get the beam of light coming from the Crystal Receiver through most of the room. Follow the beam to the Northern Crystal Prism. Rotate it three times to get the beam to pass over to the East to the next Prism. Rotate it much the same until the beam of light carries to the next crystal. Follow the beam to the South along the next several crystals. Expect to give each several rotations. After a few crystals you will see it jump suddenly through 3 Crystal Prisms at once. Head to the Southern most illuminated crystal prism. Rotate it so the beam goes to the East. This will carry the beam over to the Northern receiver and destroy it:
Head for the other side of the room. It is time to deal with the second Crystal Emitter. Interact with it to get the beam going. Follow it to the North and rotate the crystal prism so the beam goes to the West. This will send the beam down a chain. Head to the farthest part of it to the North at the end of the beam. Get the beam going to the Southwest. Head to the Crystal Prism by the South Receiver. Just rotate it until the receiver is destroyed.
Head to the center of the room. You will find King Laloriaran Dynar: