|Weapon of Mass Evolution|
At the end of Forest for the Trees after Tygrif was banished back to the Darkness Civilization with some of the Rumbling Terrasaur horns, The Choten told Nigel that he had gained new allies in the Darkness Civilization as Megaria showed up. It is implied that Megaria helped The Choten get the tanker out of the Darkness Civilization.
It is not referred to again until Siege, where the tanker of the serum was used to fill the Evo-Serum Bomb. Reef Prince Glu-urrgle in his evolved form tried to disarm it and failed. It was dropped on the Null Zone, evolving a multitude of creatures that were in its range.