Xaaron

Xaaron was a Herald of Unicron who served The Fallen. Tokimi eventually killed him in order to protect her sister and the crew of Tsunami-fune.

History
Xaaron and his brother Xintun were at some point recruited by The Fallen to serve him as Heralds of Unicron. The Fallen, who remained trapped in an interdimensional prison, ordered the brothers to find and feed him a powerful life form so that its energy would empower him enough to break free. Xintun thought that Ynot would be a suitable candidate, so he brought him to the dimension while Xaaron watched. However, before Ynot could be fed to The Fallen, he used a mask to turn Xintun into a Hollow and escaped. Xaaron decided that he had no choice but to feed his newly-empowered brother to The Fallen, whose energy empowered the titan enough for him to escape.

Soon after these events, Blackout used the Vahi Cube to rewind time in the Original Universe by six months, but because Xaaron was outside of the OU at the time, he was not affected and his brother remained deceased.

Later, Ynot had the Toa Idiotas find Xaaron in order to summon The Fallen to aid him in the fight against Blackout. (Records of these events were lost in the Great Dataclysm.)

In 150,080 CMT, Xaaron worked with The Fallen to resurrect Unicron. Xaaron was present inside The Fallen's fire dimension when Sideways delivered the four objects required to resurrect the space-god. Sideways handed the objects to Xaaron, who was then commanded by The Fallen to perform the ritual. Xaaron did as he was told and placed the objects inside the altar, which succeeded in returning Unicron to the universe.

Unicron materialized above BZPower and began attacking its residents, so The Fallen followed, but promptly had his right arm severed by Washu, who fled the scene in Tsunami-fune. This infuriated The Fallen, so he sent Xaaron and six other Heralds (Blackarachnia, Galvatron, Obsidian, Razorclaw, Sideways, and Strika) to kill her. However, Tokimi intervened and disintegrated all seven of them before they could harm her sister.

Trivia

 * Xaaron was named after a Transformers character of the same name. However, they share no other connection beyond that.