The Black Mamba was a cape made for Megamind created by Minion before their quarrel. It was wore on his back and was high-collared with blue at the back and spikes on the back of its look.
Looks[]
Completely normal[]
When Megamind's cape was normal, it had no tears on it.
As Metro Man in The Button of Doom[]
Although Megamind also had Metro Man's white cape in Megamind: The Button of Doom, he didn't need to be a hero and wore it along with his suit.