This quest is not available in game.
King Jokkum in Dun Niffelem wants you to enter the Halls of Lightning and defeat Loken. You are then to return to King Jokkum with Loken's Tongue.
One way or another, Loken shall fall.
If I have to rip him limb from limb myself, he soon shall pay for his wretched deeds.
Should you meet with him before I do, the honor and glory of his defeat shall be yours.
Return to me with his lying tongue, and earn my blessing and gratitude.