Originally Posted by
Alkhara Majere
He appeared before the royal Court of King Terenas of Lordaeron, and to Antonidas of Dalaran, and also to Prince Arthas and Jaina in physical form. He did eventually appear to Thrall; the night elves Malfurion Stormrage and Tyrande Whisperwind; and Jaina; in a dream, but Medivh, the Last Guardian of Tirisfal, was indeed not a spirit.
His choice to remain uninvolved directly in the Third War led some to believe he was a ghost. However, Medivh had been resurrected by his mother using the last of her magic when it became clear that a new threat loomed over the world of Azeroth - a threat in the form of the Scourge, the latest weapon of destruction devised by the Burning Legion. Aegwynn had survived the battle with Medivh, who promptly set up magical wards to ensure that his mother lived in peace. (check out the novel Cycle of Hatred, it short and contains this. Good book.)