An ancient and clever giant, Thronis is a Sky Giant and several times larger than a fog giant. He lives atop Stormcrag at Wyrmroost and is a gifted sorcerer. In addition to his brute strength, he demonstrates mental prowess and can temper the climate through the use of a dark orb. A white orb allows him to gaze over all of Wyrmroost and even beyond the walls without leaving his fortress.

He looks like an ordinary man except for his size. His wide mouth, longish nose, salt-and-pepper eyebrows, and gently sagging body give him the appearance of being in his mid-sixties. He wears a white toga and an enchanted sliver collar around his neck, which forces him to always be truthful. His native tongue is Jiganti, but he speaks English fluently, along with several other languages.

He is described as several times larger than Fog Giants, and enjoys a civil and proud existence. He is cordial to the team of adventurers, though he does still threaten to make a pie out of them. Eventually, he ends up helping them find their way to the Dragon Temple. In return, he asks that they bring him five figurines, a ruby dragon, a marble snow giant, an emerald chimera, an onyx tower, and an agate leviathen. Thronis keeps the dragon, the giant, and the chimera, giving the rest to Seth. Thronis told Seth that wearing his full armor, he could best any Dragon at Wyrmroost in a battle, save perhaps Celebrant himself.

Thronis has a dwarf named Zogo as a servant, along with Griffins.