The Zillo Beast might be one of the most tragic creatures in Star Wars: The Clone Wars. The Zillo Beast's home on Malastare is destroyed as collateral damage when the Republic uses an electron-proton bomb to fight against the Separatist army. After he attempts to defend himself from the Dug forces and the Republic army and is captured. Ripped from his home, the Zillo Beast escapes from captivity on Coruscant and goes on a seemingly senseless rampage. However, the Zillo Beast's rampage might have had a stronger purpose. Sensing that Sheev Palpatine was a Sith Lord, and the Zillo Beast ran amok in an attempt to warn everyone.
In "The Zillo Beast Strikes Back" featurette on StarWars.com, Dave Filoni explains it was George Lucas's idea to have the Zillo Beast focus its wrath on Palpatine instead of following the common monster movie trope of the monster falling in love with the female lead. Filoni states that he joked with Lucas, arguing "the Zillo Beast, the whole time he's trying to tell everybody that Palpatine's a Sith Lord. He knows, like, he can sense that kind of thing. And he's yelling and screaming that 'No! He's a Sith Lord...Look! He's bad!'" Thus, under this interpretation, the Zillo Beast has a specific mission to try to save the Republic from Palpatine.
While Filoni frames the theory as a joke, the Zillo Beast's actions throughout his time on the show do support this interpretation. The episode "The Zillo Beast" establishes that the Zillo Beast is an innocent life form. According to the Dugs, Zillo Beasts massacred the Dugs' ancestors, and the Dugs argue that the Zillo Beast must be slaughtered to prevent more deaths. However, this particular Zillo Beast has lived on Malastare without bothering anyone for a very long time. He only attacks in self-defense, and the episode clarifies the Zillo Beast wouldn't have harmed anyone if people just left him alone. Thus, the Zillo Beast is not a violent monster at heart. Instead, he is the victim of Palpatine's cruelty.
The Republic forces transport the Zillo Beast to Coruscant, and Palpatine's proposed plan is for Doctor Sionver Boll to study the beast and create new armor for the Republic's forces. The Jedi protest this plan, and Mace Windu argues for the Zillo Beast to be relocated to a new planet where he can live in peace. While observing Voll's experiments on the Zillo Beast, Palpatine reveals that he wants the Zillo Beast killed. He frames the order as a sacrifice for the safety of the Republic. Notably, even Senator Mas Amedda, one of Palpatine's most sycophantic supporters, questions Palpatine's murderous desires. Voll also protests, believing the Zillo Beast is an intelligent life form. The Zillo Beast's intelligence becomes clear throughout this conversation. He reacts strongly when Palpatine orders the murder. Throughout the episode, multiple scenes focus on the Zillo Beast's eye as he observes Palpatine. These moments could be interpreted as the Zillo Beast sizing Palpatine up and recognizing his is evil.
Despite the destruction the Zillo Beast causes, the writers show throughout the episode that the Zillo Beast is not actually the aggressor and might have latent Force abilities. When the Zillo Beast escapes from the laboratory, he does not attack the scientists and Clone Troopers there. Some of them are injured by debris, but their injuries are collateral damage and not a conscious attack. As the Zillo Beast travels through the Coruscant streets, he only purposefully destroys ships that actively attack him. Bystanders are harmed because Coruscant was not built to accommodate a Zillo Beast, not because he seeks to harm anyone other than Palpatine. As the Zillo Beast traverses Coruscant, his uncanny ability to sense where Palpatine is located suggests some kind of extrasensory tracking ability. It is not unreasonable to argue that this ability might be tied to the Force. If so, then it also is possible that the Zillo Beast could sense through the Force that Palpatine is a Sith.
Thus, it is entirely plausible that the Zillo Beast was trying to save the Republic from Palpatine's treachery and was killed for his efforts. After the Beast's death, Anakin says, "It is a tragedy that the Zillo Beast paid with its life for our mistakes." Palpatine's actions throughout the episode show that the Zillo Beast's death was not a mistake. Instead, it was the result of an actively cruel campaign by Palpatine to murder the Beast. Thus, the Sith killed the Zillo Beast, and he remains an unsung hero of the Clone Wars.