Trolls in "Homestuck" are members of a species of gray-skinned insectoid aliens that originate from one of the universes featured within the webcomic. The troll characters focused on in the webcomic are a group of 12 adolescents, their descendants and their ancestors.
Each of the 12 main troll characters are associated with a particular zodiac sign and wear that sign's symbol on their shirt. The zodiac signs also figure into each particular character's appearance and interests to a certain extent. For example, the character who wears the Sagittarius symbol, a constellation that represents a half-man, half-horse figure, is obsessed with horses. He is close friends with another troll who wears the Leo symbol. As Leo is a constellation representing a lion, that troll is obsessed with cats. The main trolls live on a planet named Alternia and cooperatively play a game called Sgrub that has reality-warping properties. They also communicate with a group of four humans who are playing a very similar game named Sburb in their own respective universe.