The Staff of Magnus (Skyrim)

Part one
Mzulft

Part Two
Labyrinthian

Upon entering, you find a charred corpse holding a soul jem and Tattered Note. Upon nearing the corpse, four staves rise out of slots in the ground before you. The note reads:

"Enter Twice - Exit Only Once Alteration will lead you to Destruction Only Illusion shows the way to Restoration Conjure not, but be conjured instead"