Mistaké

Mistaké (alternatively spelled as Mystakе) was the major supporting character in Ninjago. She was an ancient Oni disguised as an elderly woman, who owned a tea shop within Ninjago City. Mistaké once lived in the First Realm alongside her fellow Oni, and was later dispatched to kill the First Spinjitzu Master, but after seeing the beauty in the realm he created, she redeemed herself. Over the years, Mistaké witnessed much of Ninjago's history, including the end of the Serpentine War. She was acquainted with Wu, a son of the First Spinitzu Master, and occasionally provided him and others with various types of tea with special powers.

When the Sons of Garmadon sought to resurrect Lord Garmadon, Mistaké provided the Ninja with knowledge about the Oni and dragons. She later helped save Lloyd after his nearly-fatal battle with his father, and motivated him to lead the Resistance after his friends were seemingly killed. During an attempt to seize Garmadon's power, Mistaké revealed her true Oni form and battled the dark lord. She was ultimately overpowered and killed, though her actions helped the Ninja claim victory.