You get the key from the imp later - to let you finish the SECOND summoning quest.

Try dropping all the items for the first quest OUTSIDE the summoning area and then picking them up if the instructor doesn't recognize that you have them. Make sure you have the right rune (wisdom).

The ingredients go in the circle - the rune does NOT - it is handed to the instructor.

Reality is for those who cannot cope with fantasy. Fortunately, I can cope quite well.