Trolls are giant Bosses that can be destroyed by S dragons and higher, they amount of times necessary to hit them varies within size tiers. They spawn in different places, although most of them are scripted to happen. These enemies are very strong and can be very dangerous to small dragons. They mainly attack with their club by swinging it down in an attempt at hitting the player, or by stomping. Their club swing can hit the player's dragon if they are above the troll.
Trolls will attack the player on sight if they are in their aggro zone. They won't chase the player, but rather stay still and defend their ground.