Prior to the scratch, the trolls were a peaceful race with no need for constant violence and war. The species had a caste system where the higher caste trolls would aid and care for the lower (and more populous) castes. The heiress to the Beforan throne ran away from her duties and hid on the moon where she found a game. Just before the destruction of their race, she and eleven other trolls, with their Ancestors' legacies inspiring them, played the game. However their culture left them unable to handle the difficulty of the game.
Beforan Sgrub session (Cannon Timeline):
The pre-scratch trolls were unprepared for the difficulties of the game. A lack of leadership and the presence of sabotage caused them to fail their session. Unbeknownst to them, their session was affected by a glitch caused by Lord English that had rendered the session unwinnable by preventing them from being born in their session. After three sweeps (6½ years) in the null session, some of them sought the advice of Echidna, the mother of all monsters, who gave the trolls a choice: they could either do nothing, and doom their race to extinction, or they could have a second chance to complete the game. They chose the latter, and thus activated the scratch, completely resetting the parameters of their universe, becoming the ancestors in the new incarnation of their universe. Before completing the scratch, Meenah, on the advice of the horrorterrors, killed them all using a bomb with the same appearance as the Tumor, allowing them to continue existing as ghosts within the dream bubbles.
After the scratch the twenty four trolls arrived in different time periods of their planet's history than before to live out new lives with no memory of their previous roles. However as a result, Doc Scratch came into being. He shaped and manipulated the troll race into the warlike people they are, in order to shape the twelve kids into a group who would be able to finish the game with ease. However, the twelve trolls who originally played the game would not be the ones to play it again, but rather their ancestors would be the players, and they themselves would be the ancestors. Eventually nearly all the trolls die from the Vast Glub, a psychic wave from Feferi's lusus, a horrorterror-like creature that Doc Scratch provided to the planet. The only survivors, besides the 12 trolls players (barring Sollux's original body), are the Handmaid and the Condesce. The Handmaid later sacrifices herself to the Condesce, so that she can replace her as English's eternal servant.
Alternian Sgrub session
The trolls have completed their Sgrub session, originally starting as two teams of six players, which soon turned out to be both parts of the same chain of 12 players. The trolls at first began to question the nature of their two-team structure when the Red Team's prototyping began to affect the Blue Team's enemies and vice versa. Then, because of a Mobius Double Reacharound, the two chains turned out to be joined together all along; therefore, one Prospit and Derse, one Skaia, one pair of kings and queens, etc. exist in their Incipisphere. However, they have two Frog Temples for an unknown reason.