"Zarkon is Dying" is the eighteenth episode of the first season of the first installment of the Voltron franchise, Voltron: Defender of the Universe. It originally aired in 1984.
Lotor approaches Haggar's rival Zandra to give him a weapon and is supplied with a potion that will transform plants into monsters, just before Zarkon suffers a terrible disease. Haggar claims the cure is an Arusian fruit. Lotor is reluctant to go, thinking it is trickery, but leaves armed only with his potion when Haggar offers to prove her loyalty by sending armed forces. On Arus, he transforms a group of trees into menaces which terrorize the Voltron Force, intending to take advantage of the situation and capture Allura along with some of the fruit.