Siren

Within the universe of Borderlands, Sirens are women 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, as revealed by Handsome Jack. 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. The Borderlands 3 developer trailershowcases two more Sirens: Tyreen Calypso, who seems to be involved with the Children of the Vault, and Amara, a Siren who has the ability to summon mystical sets of arms.

As of Borderlands 3, two Sirens were revealed: Amara and Tyreen Calypso. However, Maya hints at the possibility of Ava being a new Siren.

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 player 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, which is often seen when Maya uses her power, Phaselock, but this could be because her right arm is always holding a weapon. 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 and heal herself. This is also seen when Handsome Jack uses Eridium to increase Angel's powers. Overconsumption of the material will have negative side effects. Lilith shows signs of addiction to the substance. Angel, being fed enormous amounts over a long period of time, 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 bubble made of energy from another dimension.

Angel uses an ability that she refers to as Phaseshift. The ability allows her to change the way her environment looks.It can be seen in her introduction cutscene in Borderlands 2, as she phases one of the Control Core chambers away. Later, during the fight in the main chamber, Angel is able to spawn ammo boxes for the players. By being connected to all of Pandoras' datastreams, Angel is able to open doors and hack computers or consoles, like the Catch-A-Ride station. She also claims to be able to "look forward and backward along the timeline," during the mission Destroy The Destroyer.

Other known traits 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. Maya is implied to notably lack this ability by Angel. However, no explanation is given for this.

Trivia

 * The Sirens draw their name from the Sirens of Greek mythology; according to legend, Sirens were a group of extremely dangerous human sized vultures with human heads whose faces constantly changed. They lured sailors to their death by seducing them 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, but this is likely because she never was shown using her abilities.
 * The connection between the sirens and the Eridians is further demonstrated in Borderlands The Pre-Sequel. While the player is working their way through the Eleseer map towards The Vault, it is revealed that Lilith had been following the player the whole time. The Guardians made no effort to stop her, and she says it was 'almost as if they wanted her to get to The Vault'
 * The theme of sirens was also presented in Borderlands comics, thus events depicted in comic series aren't part of Borderlands canon universe.
 * In the Borderlands Origins #2 "Lilith" comic, upon her father's death a young Lilith is visited by a very old siren who tells her of her powers and that there are others in the universe like her. She promptly dies, but the comic shows the other known sirens, and two mysterious figures in hoods.
 * In the Tannis and the Vault comics, the fifth siren Asha greeted vault hunters that came into Fyrestone on Marcus's bus until she was caught in an explosion and fell into a coma. She went by the name "Tate" and was under the care of Tannis while in her coma. She was completely brain dead, and it is unclear whether or not Tannis had anything to do with her revival. She later awoke and helped the Vault Hunters and Tannis retrieve that last piece of the vault key from a Rakk hive. She did this by using her powers, which according to her, grant her the ability to "control the beasts of any planet".