Madrigus was a dragon and a former member of the Dragon King Celebrant's personal guard. He was massive and dark gray with bull-like horns, straight, curved, and hooked spikes, plate-like scales, and a clubbed tail. While not as long as Celebrant, Madrigus had more overall bulk.
During the Feast of Welcome, which he interrupted by formally challenging Celebrant for his crown, he and the Dragon King traded barbed words, where Madrigus admitted to "encouraging" two other Dragons, Podenholm and Rondet, to challenge Celebrant in order to study Celebrant's fighting skills and tactics, and that he had come to view Celebrant as weak.
They engaged each other in a duel to the death where, despite being initially outmatched, Madrigus surprised Celebrant with the breath weapon of dark corrosive smoke called the seething night that can eat away any material, even Dragon scales, which he used to injure Celebrant.
In the end, however, Celebrant was victorious and viciously killed Madrigus with a bite to the base of the skull, crunching down to break the bone, and breathing white fire into the wound for good measure, the flames erupting from Madrigus' eyes, nostrils, mouth, and earholes. The Dragon King declared that for his treason, Madrigus' body would not be given proper respects, and his bones would be spread across Wyrmroost. Later, Tanu risked the opportunity to acquire never-in-a-lifetime potion ingredients from Madrigus' corpse and successfully made it back alive.
- Wrath of the Dragon King (Dragonwatch #2)