Obsidian

Obsidian was a Herald of Unicron who was killed by Tokimi.

History
In 150,080 CMT, the Fallen summoned Obsidian and six other Heralds of Unicron (Blackarachnia, Galvatron, Razorclaw, Sideways, Strika, and Xaaron) to help him kill Zev Raregroove and his friends, because they were attempting to prevent Unicron from consuming BZPower. Obsidian followed his allies into the seventh dimension, who began travelling through it to Zev's location, but they were intercepted by Tokimi along the way. In order to protect her friends, Tokimi used her powers of entropic balancing to destroy all eight of them. The Fallen, however, came back somehow... but he always comes back.