Tasmanian Devils are one of the few species on Mobius that don't share the same intelligence as most Mobians, despite once having been the most advanced culture in Downunda. The vast majority of the race has been transformed into savage Mobini, commonly known as Devil Dogs.
During ancient times, a group of Echidnas from Albion arrived in Downunda during the Forgotten War with the mission to develop means that the Albion Knights of Aurora could use to fight the Order of Ixis. Proving to be corrupt, they instead used genetic engineering to transform a tribe of Tasmanian Devil Mobians into less intelligent vicious dogs, which they used as beasts of burden and for guards. These Echidnas were subsequently punished for their crimes, but the damage had been done, and the race ever after recited the story of the Echidnas crimes to their children. The so-called "Devil Dog" Mobini version of the species became more and more prevalent as the generations passed, whilst the former Mobian version all but disappeared. Thrash is one of the only known examples of a sentient Tasmanian Devil left on Mobius, and most outsiders believe that the Devil Dogs are the natural form of the species. Ruins of the Tasmanian society remained in Downunda as a testament to the failing race. (StH: #246, SSSM: #2, SU: #11, CSE).
The rest of Mobius came to belief that the Tasmanian Devils had never fully evolved like other Mobians, and they apparently had no qualms about putting them to use. Their keen sense of smell makes them good for tracking scents, so they were used by Geoffrey St. John, Smiley, and Fleming to help find the prisoner Sonic the Hedgehog after he escaped from a crashed plane headed for the Devil's Gulag. Whatever his feelings regarding his people's use in such ways, Thrash would serve the Kingdom of Acorn in his own way by briefly teaming up with the Downunda Freedom Fighters and Chaotix against the Downunda Dark Egg Legion. (StH: #48, SU: #11, #12)
Accompanied by a pack of Devil Dogs-including his two sisters, who were Devil Dogs born in the same litter-Thrash set out on a quest to find and punish the Echidna society for mutating his people. His quest eventually led to the banishment of all but a handful of Echidnas to parts unknown through a Warp Ring. As a result, however, Thrash and his pack became embroiled in battle with Knuckles the Echidna and Team Fighters in the Echidna homeland of Albion. After a fierce conflict, Thrash's pack was trapped in an enclosure by Team Fighters, who later released them so they could help fight the Krudzu Hybrid Hydra, while Thrash himself escaped but was pursued by Knuckles. Thrash considered his actions just, and felt that being left the last surviving members of their Mobian races made him and Knuckles equal. Their battle led them across Mobius, including to one of the Tasmanians' ruined settlements. Here the pair encountered another surviving-though ancient-Mobian Devil and a group of Devil Dogs, before pursuing their battle to White Acropolis and then to Shrine Isle, at which point Thrash made his final escape. (StH: #244, #245, #246, CSE)
- With the exception of Thrash, the Tasmanian Devil species-notably the Devil Dogs-bear a striking resemblance to the Looney Tunes character known as the Tazmanian Devil, or Taz for short. The belief held by Mobians that Tasmanian Devil Dogs never evolved to the same level of intelligence of other Mobians-due to their genetics being modified-may be a nod to the fact that Taz is one of the only anthropomorphic Looney Tunes characters who traditionally behaves in a savage and animalistic manner rather than exhibiting many traits of civilized intelligence.
- The fact that so few Mobian Tasmanian Devils exist on Mobius could be a nod to real-life Tasmanian Devils, which are, in fact, classed as an endangered species.
- Tasmanian Devils are natural predators to Echidnas, hence why Thrash has hatred towards all Echidna kind.