On the second floor of a ruined building in Roshamuul, east-northeast of the depot, slightly north of the central mountain
His full name is Morax Astrolabius. There are 2 versions of Morax. The main NPC is north of the central mountain. The other Morax is within a dream, and you can only arrive there by using the bed with Essence of Dread or Essence of Wishful Thinking.