Shadows

Shadows are a type of ethereal being featured in LEGO Ninjago: Masters of Spinjitzu. They can be formed from anyone's shadow through dark magic, becoming a featureless black copy of the template with glowing red eyes. Armed with whatever weapons their template was holding at the time, Shadows are invulnerable to physical blows and capable of duplicating themselves.

History
In "King of Shadows", Kai chased after Lord Garmadon, who was disguised as Nya, into the Fire Temple. Lord Garmadon persuaded Kai to remove the Sword of Fire or the real Nya would fall into a pit of lava. Kai removed the sword by using Spinjitzu and cut the chain holding Nya, setting her free. Kai's shadow then materialized before him, trying to strike at them. As Kai attempted to counter the attack, Lord Garmadon summoned more shadows, who proceeded to attack Kai until he dropped the Sword of Fire. Sensei Wu joined the fight using his own shadow, attacking the shadows and using his hands to create the shape of an eagle, scaring them away.

Later, in "The Green Ninja", Kai mentions that Lord Garmadon cheated by using his shadow.