This colossus, along with the Ulduar Colossi, are possibly the largest living being ever seen in Warcraft. The Colossus' defensive and offensive systems are supposedly unstoppable. However, thanks to an ingenious last resort made by Bouldercrag the Rockshaper and carried out by adventurers, the Colossus was killed by captured Jormungars. Jormungar acid is the only thing that can destroy it's extremely hard "flesh".
These colossi were being built in Storm Peaks and sent to Ulduar to serve as Loken's army. As noted by the several colossi within.