There is a ring of energy on the floor in front of the Orrery (that big machine that shows the movements of the planes). Step into it and Use the Elementite to place it. You will then attacked by 2 waves of 3 mobs and then the final mob, Herald of Centius.
It is ok to ask for help. With any luck, others in the room will give a little aid.
Talk to Sylver again. He will send the Titanbane to Stonefield. Return there and talk to Ulan Hamda at the Sentry Station.