Trolls are a type of Dark Creature. Some Trolls are bulky and strong while others are small like Bubda. Some are intelligent and cunning like Nero but some are quite dumb like the Mountain Troll Udnar.
In Secrets of the Dragon Sanctuary, Nero teaches Seth about his new role as a Shadow Charmer and helps him with some of his new powers. Seth befriends the Mountain Troll Udnar at Grunhold in order to steal the Soul of Grunhold. They also meet Bubda, a Hermit Troll that lived inside of the magical Knapsack.
In Dragonwatch, Kendra, Seth, and Henrick meets the Gate Troll Grimp, who made a claim on a bridge at Wyrmroost but after Henrick revoked the claim, he called for Dire Bears that chased them for a while.
In Wrath of the Dragon King, Grippa, the Ridge Troll at Blackwell Keep, hands Seth the Sword of Tregain, a pair of Fleet Boots, and the Vial of Horrors aswell as giving Kendra the Bow of Plenty and a Sack of Gales. Later, he gave Newel the Cloak of Innocence.