This quest is not available in game.
Maintain your reputation with the Gelkis, and bring the Maraudine Key Fragment to Uthek the Wise in the Gelkis Village.
<name>, you helped us against the Magram. Now, help us beat the Maraudine! Kill the head of their clan, Khan Hratha!
To face him, blow the Maraudine War Horn. It is atop a high bluff in the Valley of Spears.
But to blow the horn, you must gain a warhorn mouthpiece. These are rare, carried only by trusted Maraudine centaur.
After the horn is blown, centaur will come. Kill them until Hratha appears.
Khan Hratha holds the piece of... a key. Bring it to me...