Watchbeasts were immense worm-like creatures native to the planet Devaron. They possessed vestigial legs that aided them in the purposes of burrowing, and two large pincers that grew from above their brow.
A weapons merchant named Orion Ferret once acquired a Watchbeast, which he named Ceasar. He was able to successfully domesticate Ceasar by way of a sonic pacifier. Some time during the Galactic Civil War, Orion deposited the Watchbeast on the garbage world of Patch-4. Orion used the wastelands of the planet for the purpose of concealing valuables and realized that the Watchbeast would make an adequate guardian to prevent scavengers from uncovering his wares.
Shortly after the Battle of Hoth, Luke Skywalker and Lando Calrissian purchased four black market Imperial TIE/LN starfighters from Orion and arrived on Patch-4 to pick them up. But to their surprise the Watchbeast, Ceasar, rose up from beneath the ground and attacked them. Luckily, Luke learned about Ferret's sonic pacifier and retrieved it from their borrowed shuttlecraft. He was able to use it to put Ceasar to sleep.