Siren

Within the universe of Borderlands, Sirens are females with mystical, unknown backgrounds and incredible powers, and are distinguishable by the tattoos running down one half of their body.

Only six Sirens can exist at any given time, and at the time of Borderlands 2 ' s release, three are known: Lilith, Maya, and Angel. Outside of the games, Borderlands: Origins issue 2 confirms fan speculation that the Crimson Lance leader Commandant Steele was the fourth Siren until her death.

Sirens
There are reportedly six Sirens in existence at the time that the events in Borderlands take place. The player character Lilith is one of them, and part of the reason that she is on Pandora involves searching for another whom she believes to be on the planet. The Siren she seeks is most probably Commandant Steele, due to Steele being the only known siren besides Lilith during the story of Borderlands. A third Siren to appear in the Borderlands series is Angel from Borderlands, an enigmatic character who was confirmed as a Siren in Borderlands 2. The full extent of Angel's abilities are unknown, however she makes references to performing a "phaseshift" when hacking technology. In Borderlands 2, one of the main characters is a Siren named Maya.

The tattoos are a side-effect of being a siren. The tattoos of all known and suspected sirens, however, only appear on one half of the body. Seemingly they channel their powers through the arm that possess the tattoos, often seen when Maya uses her power. The tattoos appear to cover them from foot to scalp, as seen in the special edition customization skin for Maya. Whether or not it is the same for other known sirens is unconfirmed.

Sirens thrive on Eridium ore, a mineral that became abundant on Pandora after the events of Borderlands. Patricia Tannis suggests that, because of their relationship with Eridium, there should be a connection between Sirens, the Vaults, and the Eridians. This connection is not between Eridium and the individual Siren, as Angel mentions that Maya has no previous connection to Eridium in ECHO recordings.

Siren powers are enhanced through the use of Eridium. This is seen at several points in Borderlands 2; where Lilith used Eridium to enhance her phasewalk ability. This is also seen when Handsome Jack uses Eridium to increase Angel's powers. Overconsumption of the material has negative side effects. Lilith shows signs of addiction to the substance. Angel, being fed enormous amounts eventually required a constant feed in order to maintain life function. She died shortly after her Eridium supply was cut off.

Abilities
Each Siren has an ability unique to themselves, albeit sharing similar characteristics. Lilith has the ability to Phasewalk through another dimension for a short period of time. This ability has been enhanced through the use of Eridium to teleport others as well as herself, and through the use of a high concentration of Eridium to amplify this trait she has also been able to phase the entire city of Sanctuary.

Maya has the ability to Phaselock enemies, rendering them completely immobile in a force bubble.

Angel's uses an ability that she refers to as Phaseshift. The extent of this ability is unknown, although she announces it whenever she interfaces to remote systems and it appears to be connected with the technology that she is interfaced with. She also claims to be able to "look forward and backward along the timeline," during the mission Destroy The Destroyer.

Other known traits, which may be common to any number of Sirens, include being able to power themselves up physically. Both Lilith and Maya can deliver empowered melee strikes in close quarters that can match or, depending on skill investments, exceed the damage inflicted by a number of the other characters' melee weapon strikes. Lilith's Phase Strike skill makes a notable feature of this talent.

Both Lilith and Angel have demonstrated the ability to charge a Vault key, thereby providing the power to activate the Warrior. Steele has also demonstrated an understanding of Vault keys, as she has been seen assembling one in Borderlands.

Trivia

 * The Sirens draw their name from the Sirens of Greek mythology; according to legend, Sirens were three dangerous women portrayed as seductresses that lured sailors to their death with their singing. This is reminiscent of Lilith, as she is often portrayed as a seductress as well.
 * All Sirens currently known are female. As the mythical sirens were female as well, likely all sirens are.
 * Three Sirens currently known have shown the ability to generate wings. Lilith's wings appear when using the Phoenix skill, while Maya's appear when Blight Phoenix is active. Angel's wings are shown when her true form as a Siren is revealed. The only Siren who never generates wings is Commandant Steele.