Covert is an anthropomorphic parasite. His first appearance is at the helm of Team Covert, a team from Sonic Heroes 2.
His general appearance is, literally, Rocket Metal Sonic, but wearing a black hoodie (like the one worn by Voldemort from the Harry Potter series) under which is a balaclava, so he can avoid being seen. However, we don't learn that it is Rocket Metal Sonic until we start playing Team Covert's storyline. Here, we learn that Covert does things on the quiet at night, and - without it being explicitly spoken - we learn that Covert's the boss of Team Covert, the Labyrinth's Minotaur and a group of previous glitches angry about their being ignored over the course of the series.
Covert is said to have a preternatural sense of time. Always, when in the labyrinth, he awakes at the same amount of time every day, even though he has no idea of when dusk takes place due to him putting himself to sleep in the Labyrinth, which is completely void of sunlight. He is also said to be learned in manners; on Labyrinth turf, he removes all his obnubilating clothing. Whilst speaking to his fellow glitches, he is generally polite so long as his orders are fulfilled.