Shadows are types of ethereal being that can be formed from anyone's shadow through dark magic, becoming a featureless black copy of the template with glowing red eyes. Armed with shadow copies of whatever weapons their template was holding at the time, Shadows are invulnerable to physical blows and are capable of duplicating themselves, although are subsceptible to blasts of Elemental energy, other shadows, and Golden Power.
Near the end of the hunt for the Golden Weapons, Kai chased Lord Garmadon (disguised as Nya), into the Fire Temple. Lord Garmadon persuaded Kai to remove the Sword of Fire to save the real Nya from falling into a pit of lava. With no other choice, Kai removed the sword and used Spinjitzu to cut the chain holding Nya, setting her free.
With the sword retrieved, Lord Garmadon attempted to claim it for his own by bringing Kai's shadow to life. Kai attempted to fight back, but the Shadow proved immune to his blows and struck back. Lord Garmadon proceeded to duplicate the Shadow into a small army, and they assaulted Kai until he dropped the Sword of Fire.
Before the Shadows could claim the Golden Weapon, Master Wu joined the fight, using his own shadow to fight the Shadow warriors. After fending off several attacks, he created an eagle shape with his hands, scaring the Shadows away.
Kai claimed that Lord Garmadon cheated in their previous fight by summoning Shadows to do his bidding.
The Ninja of the present and the Master Wu of the past worked together to preserve the past from Lord Garmadon's tampering. When Past Kai was lured to the Fire Temple, Present Kai explained to Past Master Wu that Lord Garmadon was going to summon Shadows to fight Past Kai after he saved Past Nya. Instead, the shadowy villain summoned his own future self to battle Past Kai, forcing the Ninja of the present to intervene.
Following his loss of the Teapot of Tyrahn, Clouse eventually sought to conquer Ninjago by plunging it into Darkness, and thus summoned an army of Shadows modeled after Bat-like creatures to assist him. After taking notice of the young YinYang Dragon named Bandit, Clouse sent the Shadows after him. Kai and Nya, confronting the Shadows, succeeded in escaping aboard the Destiny's Bounty 2.0, and with the help from the other Ninja managed to fend off the creatures. However, despite their best attempts, the Shadows took advantage of their distraction to whisk Bandit away to Clouse's lair.
Later, when Kai and Nya arrived to rescue Bandit, the Shadows succeeded in delaying them, allowing Clouse to continue the spell. With his spell reaching its final stages, Clouse had his Shadows converge onto Bandit, slowly corrupting him into a sinister Shadow Dragon. However, when Kai, Nya, and a group of friends sent by Master Wu encouraged and supported Bandit to conquer the evil inside him, the young dragon succeeded, dispersing the Shadows from his heart and instead growing into a Light Dragon.
Having succeeded in corrupting the Temple of Light with Dark Matter, Clouse summoned a small army of Shadows modeled after villagers and Samurai to help the Sky Pirates defend his plans from the incoming Ninja. However, when Master Wu arrived within the Golden Mech, Clouse had the Shadows converge onto him in order to form a doppelganger Shadow Mech to combat his nemesis. Despite the strength of the Shadow Mech, however, its blade was quickly shattered by the Golden Mech before being destroyed by its raw, Golden Power, dispersing the Shadows yet again.
- During his time in the Underworld, Lord Garmadon could manifest in a form resembling a massive Shadow of himself. It is unclear if this state had similar abilities to the Shadows Garmadon summoned to battle Kai.
- Lord Garmadon's shadow form underwent a visual makeover between the pilot episodes and "Wrong Place, Wrong Time" — notably, the whole form became somewhat darker, and the helmet was narrower.
- A Shadow's level of intelligence is unclear, as it does not speak. Kai's Shadows displayed fighting abilities on par with their template, but it is unknown if they are sentient or simply puppets of Lord Garmadon. Interestingly, the shadows used by Clouse in Realm of Shadows, modeled after Bats, acted like animals, indicating their intelligence is based on the template they were modeled after.
- It is unknown if the ability to summon Shadows is also found in the Master of Shadow, or just in Wu, Garmadon, and Clouse.