Jestro is an evil jester. His costume's main colors are red and purple. His face is white, with an large grin and several uneven teeth. His eyes are yellow and he wears clown lipstick. His outfit is tattered and torn, with skulls and boots on it. He has a damaged cape and a staff with a jester-hat topper. He wields the Book of Monsters, which summons lava monsters into the Kingdom of Knighton.
Jestro, the clumsy jester, performs at the royal court. Juggling all sorts of things. Even a smartphone?! Suddenly, the first time in a long, long time, Jestro finally gets a laugh out of the King and Queen. Unfortunately they are not laughing at him, but at something they have seen on their tablets. Jestro withdraws to the shadows and starts plotting for revenge.
Jester is the main antagonist of the Nexo Knights theme. In the TV series, it has been revealed that he was once an ordinary, if not rather self conscious and shy, jester until the Book of Monsters convinced him to become evil. He and the book then summoned the Lava Monster Army into the Kingdom of Knighton to destroy the Nexo Knights. Clay, one of said knights, was actually a friend of his, who tried to encourage and help him before his unsuccessful performance that caused a power outage.
- His name is a pun on "jester".
- His appearance is similar to The Joker and Harley Quinn from DC Comics.
- He shares some resemblance to Krazi from Ninjago.
- It has been observed that Jestro's toy figure looks a bit different than his appearances in promo videos so far, as the figure has his Jester cap's flairs drooping in the traditional fashion, while in the videos, they are pointed upwards to resemble horns.
- He has the same voice actor as Kai which is Vincent Tong.