Demlins, fearsome beasts, were indigenous to the planet of Batuu.
These creatures, of moderate size, possessed reddish-brown, scaled hides, prominently adorned with sizable blue and purple scales across their backs and upper limbs. Distinguishing features included a quartet of blue eyes and a mouth filled with razor-sharp teeth. Their elongated arms terminated in hands equipped with four formidable claws each. A lengthy tail, patterned with alternating black and white stripes, completed their anatomy. Demlins moved on two legs, their feet bearing three sharp claws.
Known for their aggressive nature, Demlins were prone to both biting and clawing. They preferred shadowy environments, such as caves, and often launched coordinated attacks. In combat, Demlins typically adopted a hit-and-run strategy, taking turns to strike before leaping back to safety, slashing at foes with their sharp claws.
During the era of the High Republic Era, certain Demlins dwelling on Batuu were corrupted by an Ancient Sith Runestone, which amplified their inherent aggression and ferocity.
In the High Republic Era, around 232 BBY to 233 BBY, Jedi Master [Sylwin] discovered an Ancient Sith Runestone and brought it to the Jedi temple on Batuu to study with Master Cohmac Vitus. The dark artifact caused the Jedi to turn against each other, leaving Mirialan Padawan Ady Sun'Zee as the only survivor. It also corrupted multiple Demlins in the surrounding area. These Demlins attacked Ady at the entrance to the temple where she fought off and killed many of them. Just as one final Demlin was about to attack, Jedi master Yoda appeared and threw the Demlin out of a window easily with The Force. Yoda then entered the temple through the main entrance, while Ady entered through the caverns. More Demlins had found their way into the temple and attacked Ady in the Main Hall, entering through the balcony doors. Ady and multiple Jedi Temple Security Droids fought them off, Ady destroying the entrances to where the Demlins were coming from and killed the remaining creatures. Ady later experienced visions of Demlins attacking her and Yoda until they managed to contain the power of the relic, pushing back the darkness together.
Around 34 ABY, a droid repair technician had a confrontation with numerous Demlins within the caverns of Hissiq Springs while battling the Guavian Death Gang. This occurred after the Utai droid technician Mubo tasked them with retrieving two crates. Subsequently, they delivered Demlin scales, alongside acid-spitter tails and terateak pods, to Seezelslak, the Azumel bartender at Seezelslak's Cantina, for the creation of a unique beverage. Seezelslak then recounted the tale of Ady Sun'Zee and the dark temple. Later, while searching for an ancient Sith relic for Ithorian collector Dok-Ondar, the technician encountered a lone Demlin in the caverns beneath the ancient Jedi temple.