Siren

Siren is an the Artifices in Xenoblade Chronicles 2. Both Aegises has their own Siren, Mythra uses a white Siren, while Malos uses a black one.

Story
During the Aegis War, Malos would often use his Siren to destroy Titans with it. Mythra would often uses her Siren's power without restraint, with her companions often criticizing her for doing so. When the party confronts him at the Kingdom of Torna's capital, Auresco, Malos admits he got bored of using Siren for destruction, and decided to destroy Torna, by awakening its true form and send his Gargoyles to unleash its energy all at once.

During the battle at the Soaring Rostrum, both Malos, and Mythra called upon their Sirens to do battle. After a brief scuffle, Malos urges Mythra to use her full power, when she refuses, he promptly uses his Siren to destroy Auresco. Horrified, Mythra unleashes a portion of Pneuma's power to attack Malos relentlessly before both enter their respective Sirens to continue fighting, much to Addam's objection. Eventually, Mythra manages to destroy Malos' Siren, sending them both plummeting into the Cloud Sea, but the aftershocks of their battle destroys Torna's core, causing it to sink into the Cloud Sea as well.

When Mythra reawakens at Olethro Ruins in an effort to protect Rex from Malos and Akhos, she uses Siren's power to kill both of their Blades, Sever, and Obrona.

While the party is battling Patroka, and Mikhail at the Ardanian Factory, Mythra uses Siren's power again to kill their respective Blades, Perdido, and Cressidus, enraging Patroka, and forcing the duo to retreat.

Later when the party was confronted by Jin at Genbu's Crown, Rex and Mythra attempted to use Siren's power, but Jin, using his true form has the power to control all elementary particles was able to deflect its particle cannon and overpowers the two, with Mythra reverting back to Pyra. As Jin is about kill Rex by removing the Core Crystal that is supporting his life, Pyra uses her willpower to control Siren and threatens to commit suicide with its targeting ray if he doesn't spare his life, prompting Jin to back off and she releases control of Siren and is taken by Jin.

At Gotrock Oracle Ruins, After Pyra and Mythra fuses into Pneuma and defeats Jin, Malos summons Ophion to attack the party, Siren intervenes and does battle with Ophion, resulting thee destruction of Ophion, as well as a portion of Gotrock Oracle Ruins.

As the party climbs the World Tree, Amalthus using Haze's Core Crystal takes control of Mythra and forces her to use Siren to destroy Torna, but she resists. Ultimately Amalthus lost control of her when with Poppi's help was able to destroy the amp towers on Indol using Siren's power.

In the year 20XX, several Echelon Siren models are engaged over the First Lower Orbit Station against the Savorite Rebels, which they manage to destroy a number of them, prompting the director of the station to activate Artifice Aion through the Conduit, only for them to be locked out by professor Klaus for his use for his experiment to create a new universe.

Several Siren models along with several Gargoyle models are seen attacking Alrest as Malos prepares to take control of Aion to destroy Alrest. Ultimately, just as the Conduit disappears, Rex, and Pneuma manages to uses it power one last time to defeat Aion. With the Conduit gone, every Artifice ceases to function.