Unknown to Medivh and Moroes, his darkening thoughts belonged to the dark spirit of Sargeras who began twisting his thoughts and emotions towards an insidious end. In time Medivh would become determine to stop the Burning Legion at all costs and under Sargeras's influence would discover Draenor and the Horde. Seeing that the Horde had been abandoned by the Legion Medivh felt that it would be a perfect irony to use the Horde against the Legion. Thus bargaining with the warlock Gul'dan from his chambers in the tower of Karazhan, Medivh promised to provide Gul'dan the location of the Tomb of Sargeras if Gul'dan would bring the Horde to Azeroth. And so, aided on the other side by Gul'dan's Shadow Council, Medivh opened the Dark Portal between Azeroth and Draenor.