Commandant Steele

Background
Commandant Steele is the leader of the Crimson Lance forces on Pandora. It has also been speculated that she might be a Siren, a possibility hinted at by her tattoos.

Involvement
Commandant Steele is the main antagonist in Borderlands. She leads the Crimson Lance army, the lawless fighters you encounter in Old Haven and beyond. She claims the Alien Technology she believes to be hidden in the Vault as the property of Atlas corporation and tries to take the vault keys by force after the last piece is collected.

The first time that she is seen is shortly after Sledge has been killed and the first Vault key piece has been acquired. At this point she transmits a message commanding that the vault key piece be turned over to the Crimson Lance, although the message is ultimately ignored and the adventure continues.

Her later machinations involve impeding the progress of the vault hunters, both by sending her forces to attack (in the hope of taking the vault key fragments) and by commandeering the ECHOnet. Just before the ECHOnet gets shut down it becomes clear that she is making a stronger bid for power than originally expected when Crimson Lance forces under her control are reported to be assaulting Sanctuary. During this section of the game she is seen the office section of the arena in which she forces you to battle the Crimson Lance Boss Master McCloud.

When you eventually meet her face to face the meeting is kept short; During the cut-scene, she announces that the Vault and its riches are the property of the Atlas Corporation and that you belong to her. After connecting the three pieces together and placing them in the keyhole, pieces of the surrounding ruins merge to form a portal to the Vault. Steele is under the belief she has won and begins to celebrate when a tentacle pierces her from behind and drags her into the mouth of a huge beast known only as the Destroyer.

Quotes
"The contents of the Vault are rightfully the property of the Atlas Corporation. But you? You belong to me."

Trivia

 * She bears the exact same tattoos as Lilith and might be the Siren she is looking for.
 * She also bears an uncanny similarity to the original design of Lilith when the game was announced to GameInformer.
 * Despite being killed by the destroyer, if you go to fight Master McCloud after you beat the game, she will be there yelling "Death to all who oppose us"
 * Although unlikely, she could be the one that all four characters are looking for. She could be the killer of Yujinny, Brick's sister, the person Roland is sworn to kill, and the Siren Lilith is looking for.