Rohtnax is a quest giver in Might and Magic VIII: Day of the Destroyer. He can be found in his home in Blood Drop, and gives the party the Find Isthric the Tongue quest.
His brother Isthric went to check on tobersk plants just before the cataclysm hit the Dagger Wound Islands, and is now trapped on one of the outlying islands. Rohtnax wants the party to fix the portals and bring his brother home.