Team Dark is a band of
thieves "treasure hunters" that formerly operated in the PMD-A universe, but have since moved to the OU. They're particularly fond of stealing gems.
Its members consist of:
Shadow the Espeon♂
Rouge the Swoobat♀
Omega the Golurk
Shadow was kidnapped and inducted into the team shortly after his arrival in PMD-A.
Ironically, all three members are actually weak against Dark type attacks.