Tox-En

Tox-En is a type of energon that causes nausea (to Cybertronians), paralysis, and then death. It also makes them weak and slow and the only known way to destroy it is by lava.

Tox-En was also the fourth Iacon relic to be found in season 2.

History
During the Great War, Megatron created Tox-En for his Decepticon chemical warfare to wipe out the Autobots. Bulkhead mentioned that he witnessed an entire unit of his fellow Autobots got wiped out due to exposure of Tox-En unleashed in battle. Sometime, the Autobots managed to capture a chunk of Tox-En and placed it in Iacon on a special containment unit. Bulkhead battled Hardshell and throw the last piece to Hardshell as he fell into a volcano. The Tox-En was extinguished as it melted in the lava inside the volcano.

At the war's final days when Iacon was nearly overrun, all Iacon relics were ejected into the far reaches of space including Tox-En where they soon land on Earth.

Trivia

 * Given its color and effect, Tox-En can be though of as a reference to Kryptonite, a weakness to the Man of Steel from the Superman comic books.
 * All the other relics were to be used as weapons/tools by the Autobots. Despite being willing to use the Spark Extractor, it is unlikely the Autobots would use the Tox-En. Since Alpha Trion packed the substance, it could be presumed he had a reason, yet it is still unknown.