Terrorcons are deceased Transformers reanimated through the corrupting power of Dark Energon. Reborn and glowing with the corrupted lifeblood of the Transformer race, they are little more than mindless zombies, directed (in a general sense) by the will of Megatron. While they are slow, and easily destroyed by targeting their heads, their quantity makes up their quality.
In Starscream's Energon mine, after Megatron returned, Starscream gave him the body of Cliffjumper as a welcome home gift to test the Dark Energon on. Megatron planted it in Cliffjumper's chest which absorbed the power, reactivating him into a mindless killing machine. He lashed out at two Vehicons before turning on Megatron. Megatron sliced him in half and chucks him over the side of the ledge they'd been standing on.[Episode needed]
Later, the Autobots arrived and Arcee tried to retrieve Cliffjumper. When she found him, in half, he lashed out at her and fell over the side. Arcee grabbed him, infecting herself. Once again, Cliffjumper lashed out and she let him fall into an Energon pool.[Episode needed]
Back at base, Ratchet examines Arcee, the purple substance drips on a piece of equipment. When Ratchet turns his back, it transforms into a small spider bot. It attacks Ratchet but is later killed by Optimus. [Episode needed]
After being beaten by Megatron, Starscream tried to revive Skyquake to start his own undead army. However, his attempt failed when a collision of dueling ground bridges transported the undead Skyquake into another dimension.
Starscream would later attempt to use Dark Energon in an attempt to bring Breakdown (by this time with Silas in control) under Megatron's control since the Synthetic Energon that Knockout had injected into Breakdown was causing him to act extremely violently. However, the Dark Energon reacted badly with the Synthetic Energon and caused Breakdown to mutate into a vampiric Terrorcon with a fanged maw that then ran amok through the ship, turning any troops it encountered into more vampiric Terrorcons. Eventually he encountered Airachnid's stasis pod and freed her from it in an attempt to drain her Energon. However, she was able to finally bring him (and Silas) down but was bitten in the process. Airachnid (and her Insecticons) would then be transported via Space bridge to a barren moon where she would slowly drain the Energon from her willing subjects one by one.
After Unicron reawakened, he traveled to Cybertron (in Megatron's possessed body) to destroy his brother Primus (who had also recently reawakened). In order to do so he used his Dark Energon to raise an army consisting of an entire burial ground of fossilized Predacons. Unicron and his army then proceeded to the Well of All Sparks. There they faced opposition from the Autobots and the living Predacons. Despite both the Autobots and Predacons putting up a valiant fight, the undead army moved into the Well towards Primus. Only the timely arrival of Optimus Prime with the container of the Allspark and the subsequent entrapment of Unicron within the container was enough to sever Unicron's connection to the Terrorcons and they dissolved into dust.
- Terrorcon Cliffjumper (Deluxe, 2012)
- A re-deco of the Deluxe Cliffjumper released in Wave 3. He has Dark Energon painted on him and one missing horn, as in the cartoon. The vehicle mode is unchanged except for the paint.
- Megatron calls them his "Legion". Lets hope they don't have tongues.
- In Optimus Prime's prediction of the future if Megatron brought all of Cybertron's dead to Earth, the Terrorcons are seen to fire lasers out of the palms of their hands.