Some TMNT stuff really isn't for little kids.
Just as in the 1987 TV series and Archie Comics, Tragg in the IDW comics is Krang's deputy commander and right-hand man. At one time, he and Granitor were subordinates of the tyrannical cyborg Traxus. But after Traxus was killed by Krang in single combat, they voluntarily submitted to him. They were later (probably the very first of Krang's followers) to be given their characteristic stone skin by a preparation in Baxter Stockman's workshop turning them into Stone Soldiers.
Tragg was instrumental in Krang's attempt to completely conquer the home planet of the Neutrinos, but escaped along his master after the battle, in which the END rocket from Professor Honeycutt put all of the weapons of Krang's forces out of action.
He was later involved in the battle between Krang's forces and the Foot Clan on Burnow Island. Traag and Granitor remained faithfully in Krang's service until their master's terraformer weapon, the Technodrome, was activated to turn the Earth into a new Utrominon and was one of the few there who was not killed by the terraforming that took place. Thanks to the intervention of the Turtles and the Fugitoid, the effect remained limited to Krang's earthly base of Burnow Island. Traag and Granitor survived the now toxic environment with great difficulty and were later found by the Turtles . Along with Granitor, he survived for several weeks in a cave that temporarily contained breathable air, but were slowly dying as the atmosphere changed. When Leonardo and Raphael came to investigate the murder of an Utrom, the two stone soldiers held the Turtles at gunpoint and demanded their oxygen breathers. In their weakened state, they were defeated easily by the Turtles and taken to the Technodrome, and were then attacked by the mutant Leatherhead .
Tragg was imprisoned by the Utroms for some time after that, but was freed by Ch'rell and became his loyal follower.