Smirch is (presumably) a resident of the Metropolis Zone and a thief. Somehow, at some point, Smirch managed to steal the purple Chaos Emeralds under the nose of guardian Knuckles the Echidna. Unbeknownst to him, he then tried to sell the Emerald back to the echidna before Sonic the Hedgehog intervened. Smirch managed to escape on two occasions thanks to the strained teamwork between Sonic and Knuckles, but was eventually knocked out when Knuckles punched the hedgehog into Smirch's head. Smirch seemingly got away without any further punishment.
It is unclear whether or not Smirch has magic powers. When confronted in the Metro Bar, Smirch unleashes a cloud of poisonous gas that Sonic is required to dispose of. It seems to just appear around him, but could have been a vial of the gas. Furthermore, Smirch seems to stand around it, unfazed by the idea that it could kill him. This suggests that he is immune to its effects.
Smirch is said to be faster than Knuckles, outrunning the echidna while escaping with the Emerald.