The Zillo Beast is a gargantuan monster from the Star Wars universe. It is a semi-sapient reptilian creature native to the planet Malastare and was the planet's apex predator in the distant past. It stands at 318 feet tall and sports a set of winding, flexible limbs including three arms (with one protruding from the back), two legs and a tail that ends in eight curved spikes. Its entire body is covered head-to-toe in an impenetrable hide that is immune to blasters, explosives and even lightsaber strikes.
By the time of the Clone Wars, the Zillo were believed to have been extinct, but one surviving beast emerged from a sinkhole following the Galactic Republic's victory against the Separatist Droid Army at the Battle of Malastare. When the creature's invulnerability was made apparent, Supreme Chancellor Sheev Palpatine happened upon the idea of capturing the beast for study, hoping that the monster's armour could be replicated for use by the Republic's clone soldiers. Against the better judgement of the Jedi, the beast was incapacitated after prolonged exposure to tank-mounted stun rays and was shipped off to the Republic capital of Coruscant.
While in captivity, the Zillo Beast witnessed Chancellor Palpatine and heard him mention some derogatory comments, apparently understanding him and becoming infuriated. It would later escape from confinement and go on a rampage across Coruscant, causing massive damage and killing untold numbers of beings as it made its way towards the Senate Hall. When it reached the vast dome, the creature singled out the Chancellor and pursued him, crushing anyone and anything that got in its way. By this time, Republic scientist Dr. Sionver Boll had synthesized a toxic gas from Malastarian fuel which would be used to kill the Zillo Beast. Several gunships fired projectiles loaded with the poison gas, wearing down the Zillo Beast and killing it.