After entering the Troll Stronghold, go south until you find a set of stairs going down. Follow the stairs to reach the stronghold kitchen, from where you should head north-west through 2 doors and into a room where Ug can be found. Talk to him to learn that he is in love with a female troll named Aga, who unfortunately loves another, aggressive troll called Arrg. Ug cannot gather the courage to ask Aga out, for fear of Arrg's wrath. As a good Samaritan, offer to help the poor troll, who promises not to eat you.