Ug is the chief of the Uglithug tribe and the father of Tantrum O'Ugerly. Ug also rules the Uglithug slavelands and sends many men on impossible tasks to win Tantrum's hand in marriage. In How to Steal a Dragon's Sword, it was revealed the Witch excellinor kidnapped UG, and imprisoned him in the old cabinet. Excellinor kept defeating him at chess, and threatened to kill him later, in revenge for her being imprisoned for twenty years. When UG and Stoick were rescued by Hiccup, UG ran away with the terrified Flashburn and left the Swordfighting school, never to be seen again. UG only appears in two chapters in How to break a dragon's heart despite being the main antagonist, and only appears in one chapter in How to steal a dragon's sword.
Marriage
Ug wants his daughter to be married to a person of Royal Blood. However this may not be strictly true as when he sends his daughters fiances on impossible tasks (which vikings must complete in order to be married) he lets the nearby Berserk tribe know and the Fiances are always captured.
When Ug finds out that a member of the Hooligan tribe has been sending love letters to Tantrum he demands that the person own up and be killed (unless the person was of royal blood) or all the unmarried young men in the Hooligan tribe will be killed.
Ug does get his Berserk honey as Humungously Hotshot breaks in and leaves out fours jars and pours the fifth one his slippers. Humongous also steals his daughter, a mood dragon and a throne.
Stormfly
Stormfly is Camicazi's mood-dragon which Camicazi orginally stole from Ug. Ug takes her back in How to Break a Dragon's Heart, but Stormfly shows loyalty to Camicazi and claims to have bitten that rude uglythug many many times.