Some TMNT stuff really isn't for little kids.
At one time, he and Tragg were subordinates of the tyrannical cyborg Traxus. But after Traxus was killed by Krang in single combat, they voluntarily submitted tohim. They were later (probably the very first of Krangs followers) to be given their characteristic stone skin by a preparation in Baxter Stockman's workshop making them Rock Soldiers.
Granitor commanded an assault on a Neutrino resistance bunker, to capture the Fugitoid and bring him back to Krang. Due to his command the Neutrino bunker was destroyed and many innocent Neutrinos killed along with Fugitoid's family. Later on he and several other Rock Soldiers was searching the demolished base for Fugitoid. Granitor realized that the Fugitoid was in fact Honeycutt and chased him trough a portal to Earth. However, the Fugitoid used his morphing abilities to shapeshift himself into human form and get lost in the crowd.
Granitor also presented with Trag and General Krang in Baxter Stockman's Stockgen when he scolded Old Hob for losing Splinter.