Mehkun is an NPC that used to be found in Crystal Overlook, with a still unknown purpose. He appeared as a purple spirit from the Realm of Torment and did not respond when approached. He was added in an update on December 8th, 2006 update, but was apparently removed some time around the March 13th, 2008 update.
He seems to have been added at the same time as the Cairn of Stones that had been spotted in a number of places in The Desolation, but it is unknown if there is any relationship between the two. Bahltek may have also been added at this time.