This quest is not available in game.
Maintain your Magram reputation, and bring the Maraudine Key Fragment to Warug in the Magram Village in Desolace.
The Gelkis Khan is dead, and now the Maraudine will fall! Kill the Maraudine Khan, Hratha!
To face him, blow the horn on the high bluff in the Valley of Spears. But to blow the horn, you need a mouthpiece. To get a mouthpiece, kill Maraudine centaur. Keep killing until you find a mouthpiece. Then blow the horn.
Do this and Maraudine centaur will come to the tower. Kill them until Khan Hratha appears. Hratha holds the piece of a key. Give this piece to me...