Mia Smoak

"Blackstar" is the alias of an otherwise unnamed woman who resides in Star City in the future.

Potential future
At some point she got involved in underground cage fighting as a "stress release".

Also at some point, she came into contact with Felicity Smoak and sold her technology to trigger bombs. When she first reveals this information to William Clayton, Dinah Drake and Zoe Ramirez, she says that she had no knowledge of Felicity's plan, but it’s later revealed that she does.

Abilities

 * Expert combatant/Martial artist: shown as a cage fighter, Blackstar seems to be highly trained and it allows her to beat bigger opponents.