The Driller
The largest subterranean lifeform native to Cybertron, Drillers are not to be taken lightly. Enormous multi-tentacled beasts capable of burrowing through the ground or through buildings with ease, they are capable of great destruction and carnage on any scale. Naturally, all these qualities have endeared them to Shockwave who keeps one as a pet and personal transport.
In Ultima, the Driller is used by Shockwave as a juggernaut weapon in the Organization's Decepticon Army. The beast made its debut in Classified, when a Special Society team were on an Artifact hunt, stumbled upon a trap which brought the Driller to life and initiated it's destructive program, and attacked them. And apparently, he's not the only one of his kind that still around and they can just as easily devour of his other prey.