The Trolls are recurring antagonists in the Skylanders series.
Skylanders: Spyro's Adventures
The Trolls were originally the stereotypical trolls that lived under bridges, although they originally tried to toll those that went to cross their bridges. After being fools so many times, they decided to work under Kaos as part of his military. They would often fight against the Skylanders and became war rivals with the Mabu. Two notable trolls would be Glumshanks, better known as Kaos' Butler and Boomer, a Skylander that defected from the Troll military.
The Trolls continued to work under Kaos after he returned to Skylands and would once again fight against the Skylanders.
The Trolls would enter the Cloudbreak Islands after Kaossandra appeared to help her son to 'Evilize' the Ancient Elementals and take over the Skylands.
Skylanders: Trap Team
Some of the Trolls went to branch out and help some of the other Villains while some of them continued to go to war against the Mabu. Some of the most notable Trolls being the Bruiser Cruiser, Chill Bill, Lob Goblin, Shreadnaut, Smoke Scream, Trolling Thunder and Threatpack.
In the Mirror of Mystery expansion Pack, the Skylanders enter an alternate reality where the Trolls are peaceful hippies and try to avoid fighting against the Evil Mabu.
The Trolls continued to serve Kaos by kidnapping the Mabu and sending them to the underworld so that Count Moneybone would watch over them. Some of the Trolls mainly went to prevent the Skylanders from trying to fight against the Titans.
The Trolls only appear in the Gryphon Park Observatory Expansion Pack, where they would try to hunt down the Gryphon eggs and fight against the Skylanders, only to fail.