Costa used to belong to Marshal, but Marshal released him, thinking he was too stubborn.
Costa debuts on the outskirts of Nimbasa City. Black captures him as an example to White, who was struggling with how to capture Pokémon.
Although Costa refuses to listen to Black, Black sends him out first against Clay's Krokorok; Costa easily defeats Krokorok and retreats into his shell when Palpitoad and later Excadrill attack him. His tough shell easily rebuffs Excadrill's drill.