Deep Giant is the fosterling of the Mountain King and is the second most important of the Trolls.
He led the Trolls in the Battle of the Riven Mountain, where he was killed by Lady Eiluned.
After the Sundering he united the Trolls by swearing the Oath of the Truehearts with Snow Daughter. Together the two of them, with the aid of Lady Eiluned, went to Arcadia and waited in the antechamber of the Gate of Ivory. When the Mountain King was reincarnated, Deep Giant gave himself up to the Sidhe as a hostage for the good behaviour of the Mountain King.