|“I've fought hard for this staff and will not give it up easily.”|
|— Acidius to Pythor|
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 and effectively store Venomari Venom, ensuring that his forces never have to worry about running out of venom in battle. Following their reform, he serves as an elder of the Serpentine.
During the Serpentine Wars, Acidicus and the other Serpentine attacked Jamanakai Village, though were fended off by the Elemental Alliance. The Anacondrai soon arrived and before long, Acidicus announced to Arcturus that they had taken the village.
Near the end of the war, Acidicus and the other Venomari had taken a handful of civilians hostage in the Toxic Bogs. It was there that the Maya found them and used a Sacred Flute to lock him and the other Venomari in their tomb.
Kai and Jay were sent out on a mission to investigate the Venomari Tomb, but upon reaching the Toxic Bogs, they found the tomb to be empty. As they looked around Kai was met by Spitta, who spat venom in his eyes. While Kai began to hallucinate, Acidicus and the rest of his tribe came out of hiding. Zane and Cole arrived but were quickly cornered by the Venomari and Constrictai. Acidicus laughed as the four Ninja began sinking on a log in an acid lake. However, Samurai X appeared, 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 the 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 hit Acidicus over the head with his staff, the two dropped their staffs as they engaged in a small fight. However, the venom from the staffs spilled onto the floor and mixed, giving Pythor the idea to drip the venom of each General's staff onto a sheet of paper, which revealed 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 was present with the other generals when Skales suggested that he be crowned their new leader. The Serpentine ultimately decided to ally with Lord Garmadon, abandoning Acidicus and the other generals. Skales later devised a plan to kidnap Lloyd in an attempt to blackmail Garmadon into allowing him leadership of the Serpentine. Acidicus caught Jay eavesdropping on the Serpentine's plan and had him tied up in the subway.
As part of the plan, Acidicus, along with Fangtom and Skalidor, robbed the bank to distract the Ninja. Kai, Cole, and Zane chased the Serpentine into the subway, where they attempted to escape aboard a subway train. A fight between the generals and the Ninja ensured, wherein the generals managed to escape as the Ninja attempted to stop the train from running into Jay.
Acidicus and the other remaining generals soon joined up with Lord Garmadon who presented them with his new Mega Weapon, though the Venomari doubted that Garmadon knew how to use the weapon. Garmadon eventually did figure out how to used it and inadvertently brought Captain Soto's crew back, who in turn took over the ship and threw Acidicus and the other serpentine into the brig. After the Ninja dealt with the Pirates, the Serpentine reclaimed the ship and Acidicus stood by Garmadon as he mocked the Ninja.
After breaking Skales out of jail, Skalidor drove with the Serpentine Generals in the Ninjaball Run race.
Acidicus, along with Skales and the other generals, met with Lord Garmadon at the Ninjago Museum of History, where Garmadon devised a plan to use the Mega Weapon to resurrect the skeleton of the Grundle. When Garmadon thought his plans had been thwarted by the Ninja and escaped, Acidicus and the other generals stole a Serpentine coffin. The Ninja followed them to the streets, where the generals attempted to escape through the sewers. Upon realizing that the coffin wouldn't fit through the manhole, Acidicus and the other generals escaped empty-handed.
Acidicus and the other Serpentine generals returned to Ouroboros where they crowned Skales the new snake king. They along with the rest of the Serpentine then proceeded to burrow under Ninjago City to carry out Skales's first order to take back Ninjago as their own. However their plan failed as they came across the tomb of the Stone Army just as it was awaking due to venom of the Great Devourer. The Serpentine rushed into battle, but upon realizing that the stone warriors were indestructible, Acidicus advised that they retreat. Skales however insisted they remain and fight, though the Stone Army overpowered them and left the tomb, trapping the Serpentine in there instead.
When the Ninja came to the Serpentine in search of answers about a scale they found during a previous battle with the Overlord's Nindroids, Acidicus told them of the Serpentine legend, the curse of the Golden Master.
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.
- In "The Curse of the Golden Master," his Venomari Staff is now emerald instead of golden. In addition, it no longer has the Anti-venom.
- In the same episode, he is referred to and credited as the "Chief."
- He may not always have been a Serpentine general due to the fact that he said "I've fought hard for this staff and will not give it up easily." in the show.
- Acidicus's name is a pun on the word "acid."
- Acidicus is a playable character in LEGO Ninjago: Tournament.
- Acidicus is a playable character in LEGO Ninjago: Shadow of Ronin. He can be bought for 250,000 studs after obtaining his character token in "Level 7: The Toxic Bogs."
- He and Skalidor are the rarest Serpentine minifigures as they are both exclusive to a $120 set released in 2012.
- In LEGO Ninjago: Wu-Cru, Acidicus serves as a boss in the "Venomari Tomb" level.