The Reaper of the Twin Serpent Mountains is a servant of Grenth, who governs the Twin Serpent Mountains of the Underworld. He can be found by Grenth's Statue in the Twin Serpent Mountains. For him to appear you have to destroy the Terrorweb Dryders around the statue. He can teleport the party to the other Reapers of the Underworld, as soon as they have been freed (see quest Restoring Grenth's Monuments). Take care not to let any monsters come near the Reaper. If he dies, your party will be kicked out of the Underworld.