The Great Devourer

The Great Devourer was a legendary beast and the ultimate antagonist of the first season of LEGO Ninjago: Masters of Spinjitzu. It was a monstrous snake worshipped by the Serpentine as a god, believed to consume all of creation if left unchecked. According to legend, it could only be unleashed if the Serpentine tribes united as one and found the four silver Fangblades. It was also responsible for Lord Garmadon's transformation to evil, as it bit him as a child, corrupting him with its evil powers.

Can of Worms
The Great Devourer's existence was revealed when Cole and Zane entered the Constrictai Tomb. While searching for the inhabitants, the two ninja discovered a crude mural on the wall depicting the Serpentine gathering before an especially massive snake. Zane translated the drawings as a prophecy: when the Serpentine united as one, they could find the Four Silver Fangblades and unleash the Great Devourer, who would consume all of Ninjago and turn day into night.

The Snake King
A statue of the Great Devourer was present at one end of the Slither Pit arena in the Lost City of Ouroboros.

Tick Tock
The Great Devourer made its first true appearance in a flashback Sensei Wu had before he set out to find Lord Garmadon's Dimension, when the old man told his students how Lord Garmadon's descent into evil began when he was bitten by a strange green snake in the bushes. Wu explained that the snake - a young Great Devourer - was a legendary beast that would consume all in its path, and its venom could turn even the most noble soul into a being of pure evil. He charged the Ninja with finding the four Fangblades before the Serpentine could, as the Fangblades were the keys to the Devourer's revival.

The Rise of The Great Devourer
Despite the ninja's best efforts, Pythor P. Chumsworth managed to collect all of the Fangblades and retreat to Ouroboros, where the Devourer was thought to have been imprisoned. Placing the Fangblades in the teeth of the statue overlooking the Slither Pit arena, Pythor commanded the Devourer to awaken, expecting it to emerge from the statue. To his surprise, the beast was not within the statue, but beneath the arena itself, and it was far larger than Pythor had expected.

More frightening still for the Anacondrai General, Sensei Wu revealed that the Great Devourer was not bound to obey the one who awakened it - in fact, it had no qualms about eating the Serpentine along with the rest of the world. As Sensei Wu prevented Pythor from fleeing, the Great Devourer burst free of its stone prison, immediately swallowing Pythor and Sensei Wu whole.

The Day of The Great Devourer
The Ninja attempted to escape the Devourer in the Destiny's Bounty, but they only succeeded in making the beast even bigger when it ate their jettisoned ballast and the ship itself. However, the escape gave them time to reach Ed & Edna's Scrap N Junk, where they used a Tornado of Creation to build the Ultra Sonic Raider. Equipping their new vehicle with Zane's recording of the Sacred Flute, they managed to deal some damage to the Devourer, also discovering a small weak spot on the top of its head. However, the Great Devourer destroyed the Ultra Sonic Raider's sonic cannons and withdrew to attack Ninjago City.

The Ninja followed the Great Devourer and managed to prevent it from consuming any innocent civilians, but the monstrous snake proved too powerful for them to defeat. Even the arrival of Nya's Samurai Mech and the Ultra Dragon did little against the Devourer. Eventually, Lord Garmadon arrived and revealed that the only way to slay the Devourer was to use the power of all four Golden Weapons, which only he could do. Despite their misgivings, the Ninja agreed, with Kai also telling Lord Garmadon about the Devourer's weak spot.

While Lord Garmadon left to prepare his attack, the Ninja distracted the Great Devourer, leading it on a mad chase around the city. Eventually, they were able to immobilize the beast by tangling its body in buildings and tricking it into biting its own tail, leaving its weak spot wide open as Lord Garmadon combined the energies of the Golden Weapons with his own dark powers. Declaring his actions as vengeance against the Great Devourer for dragging him down the path of evil, Lord Garmadon leapt from a skyscraper and plunged through the creature's weak spot, causing the Great Devourer to explode spectacularly.

Darkness Shall Rise
Despite its destruction, the Great Devourer's evil influence continued to plague Ninjago - literally, as its defeat flooded the city with venom. The Ninja spent a large amount of time helping the city's cleanup efforts. When Skales was attempting to assert his leadership over the Serpentine, Skalidor suggested unleashing the Great Devourer again, only for Skales to strike the Constrictai General for the bad idea.

Double Trouble
Lord Garmadon called his Serpentine forces together on the Black Bounty for a brainstorming session on how to defeat the Ninja with his new Mega Weapon. Upon hearing that the weapon could only create, not destroy, Lasha suggested recreating the Great Devourer. Lord Garmadon was not amused by the idea, and had the Venomari Scout thrown overboard as a sign of his displeasure.

The Stone Army
The Great Devourer's venom dripped onto several pieces of Stone Army merchandise at the Ninjago Museum of History, bringing them to life. Later, some more venom dripped on the Giant Stone Warrior exhibit found by Misako, bringing the ancient soldier to life.

The Day Ninjago Stood Still
More of the Devourer's venom seeped deep underground, activating an entire army of Stone Warriors sealed in a hidden tomb unearthed by the Serpentine - although this also ended with the Serpentine themselves being sealed away once again.

Abilities
The Great Devourer had an insatiable appetite and the ability to consume anything that it came across. Whenever it consumed something, it grew larger and more powerful - the Ninja noted that it would have been truly unstoppable if allowed to consume the bustling metropolis of Ninjago City.

In combat, the Great Devourer normally used its tremendous size and nigh-invulnerability to its advantage, attempting to swallow anything in its path and smashing opponents with its spiked tail. Its venom was capable of bringing inanimate objects to life and could corrupt even the purest individuals into wrathful megalomaniacs against their will.

The Great Devourer only displayed two real weaknesses over the course of the show. Like the Serpentine, it appears to be intolerant of the Sacred Flute's music, to the point of physical pain. It also has a small weak spot on top of its head - if it takes a particularly powerful blow to this point, it will be destroyed.

Trivia

 * According to Kai, the four Silver Fangblades were made from the original teeth of the Great Devourer.
 * The Great Devourer's true relationship to the Serpentine is unknown. It was considered a ruler and god of the Serpentine, but they immediately hid in fear of it when it was released, as they were avoiding the considerable threat of being eaten.
 * In one of the supplementary Ninjago comics, it is implied that the Overlord was responsible for creating the Great Devourer by corrupting a snake with darkness, thus the Overlord might be responsible for turning Garmadon evil in the first place. This theory is supported by the end of "Rise of the Spinjitzu Master"; when Lloyd defeats the Overlord, Lord Garmadon is purified of the Devourer's venom.
 * The Ninja immobilize the Great Devourer by tricking it into biting its own tail. This is another reference to ouroboros - often depicted as a snake eating its own tail - the concept of cyclical events and entities.
 * The Great Devourer's abilities and traits appear to be larger-scale versions of the Serpentine's tribal abilities. It has the Constrictai's rapid burrowing abilities, the Anacondrai's ability to swallow things whole, and the effects of its venom could be interpreted as a mixture of Hypnobrai Hypnotism and the Fangpyre's Bite.
 * Physically, the Devourer's green skin and tendency to secrete mass amounts of fluorescent green venom hearken back to the Venomari, but its long fangs resemble the Fangpyre and its pink eyes are similar to the Anacondrai.
 * The Great Devourer has only appeared in one LEGO set, 9450 Epic Dragon Battle. Physically, it bears more resemblance to the young Devourer seen in Sensei Wu's flashback in "Tick Tock", and it is significantly smaller than the Devourer seen in the show - in fact, it appears to be approximately the size of the statue in Ouroboros' Slither Pit.