Serpentine General of the Venomari tribe, he can has white spikes on his head, tusk-like fangs, and four yellow eyes. His body is dark green with black, red, and lime green markings.
The most intelligent member of the Venomari, Acidicus is responsible for most of his tribe's battle plans and schemes. He also invented special vials that can safely store Venomari Venom, ensuring that his forces never have to worry about running out of venom in battle.
Kai and Jay were sent out on a mission to investigate the Venomari Tomb, but upon reaching the Toxic Bogs, they find the tomb is empty. As they look around Kai is met by Spitta, who spits venom in his eyes. While Kai begins hallucinating, Acidicus and the rest of his tribe come out of hiding. Zane and Cole arrive but are quickly cornered by the Venomari and Constrictai, Acidicus laughing as the four Ninja begin sinking on a log in an acid lake. However, Samurai X appears, providing a rope for the Ninja to escape on and attacking the Venomari, forcing them to retreat.
When Pythor discovered The Lost City of Ouroboros, he summoned the rest of the Serpentine and challenged Acidicus and the other Serpentine Generals in a Slither Pit to claim the title of Snake King. Acidicus was punched in the face early on, but seemed to gain the upper hand when he, Skalidor, and Fangdam tackled Pythor simultaneously. However, the cunning Anacondrai uses the Sacred Flute to incapacitate the Generals (save Skales, who was secretly allied with him), and promptly defeated them with ease, with Acidicus being backhanded to the ground as he reeled in pain from the Sacred Flute's music.
The Generals began to question Pythor's plans, deciding to take their staffs back. When Skalidor accidentally hits Acidicus over the head with his staff, the two drop their staffs as they engage in a small fight. However, the venom from the staffs spills onto the floor and mixes, giving Pythor the idea to drip the venom of each General's staff onto a sheet of paper, which reveals a map of the Fangblade locations.
While Pythor searched for the last Fangblade somewhere in Ninjago, Acidicus waited in The Serpentine's Underground Fortress with the rest of the Generals. He appeared somewhat skeptical about the existence of The Great Devourer, commenting that he was curious to see what would happen when the Fangblades were united in Ouroboros. Later, after Pythor returned with the final Fangblade and imprisoned the Ninja (who were attempting to steal the other three), Acidicus was among the Serpentine reluctant to leave for Ouroboros immediately, suggesting that they at least celebrate capturing the Ninja.
When Pythor finally succeeded in awakening the Great Devourer, the Serpentine were forced into hiding when they realized that the beast had no compunctions about consuming them along with the rest of the world. Acidicus was among the Serpentine taking shelter in the Fangpyre Tomb as the Great Devourer rampaged through the Forest of Tranquility. After the Great Devourer's destruction at the hands of Lord Garmadon, Acidicus was the first to hear the cheers of the people in Ninjago City.
(NOTE: The episode shows Skalidor speaking when the Serpentine hear the people's cheers aboveground, but the line is delivered in Acidicus' voice, implying that the Venomari General was supposed to be the speaker.)
Acidicus is as dangerous as the Toxic Bogs the Venomari call their home. Victims who have been hit by the Venomari venom hallucinate and sometimes see their worst fears materialize before them.
General Acidicus is the brains of the otherwise intelligently challenged Venomari. He has cleverly constructed vials the Venomari can use for carrying extra venom in their combat gear, so they never, ever run out of venom in battle. He strongly supports Pythor’s efforts to unite the tribes and rule the world.
- He has a similar headmold to Lizaru, but with white spikes on his head instead of green.
- In concept art, Acidicus's weapon (the Hypnobrai Fangblade) has a gold blade instead of the proper silver color.
- Several cards seem to give Acidicus a prominent leadership role among the Serpentine, as he is depicted at the head of an army of Serpentine.