Samukai

"No! You will obey me now!" - Samukai betraying Lord Garmadon

Samukai was the former King of The Underworld and Lord Garmadon's head General.

Usurpation
Samukai was once the King of the Underworld until Garmadon was banished to the Underworld after losing to a fight with his brother Sensei Wu. Samukai, addressing his authority, attempts to subject Garmadon to a lifetime of pain and suffering for his wrongdoings, but Garmadon used Spinjitzu to engage into a fight with Samukai. After the duel ends with Garmadon finally defeating Samukai, Garmadon then took Samukai's helmet for himself, dubbing himself as the new King of the Underworld, much to Samukai's discomfort. Samukai then became relegated as the Skulkin General of Fire. At some point, Samukai later finds Dr. Julien and requests him to make monstrous war machines for the Skulkin army, threatening that if he wouldn't do what he was told to do, he would never see his son ever again.

Assault on Four Weapons Blacksmith Shop
Years later, he lead an assault on the Four Weapons Blacksmith shop to find the map to the four Golden Weapons. He fought Kai one on one for a small amount of time before subduing him, but before he could finish him off, Sensei Wu intervened. Samukai then used his daggers to make a large water tower begin to fall on Kai, leaving Sensei Wu with a choice: Rescue Kai, or capture Samukai. Samukai used the distraction to capture Nya and escape in his Skull Truck.

Seeking the Golden Weapons
He then went to find the first Golden Weapon, the Scythe of Quakes, hidden in the Caves of Despair. However, Nuckal read the map upside down, and was digging in the wrong place. After the four Ninja accidentally gave away their presence, he took his army in to fight them and claim the Golden Weapon. Soon after the Ninja discovered Spinjitzu during the battle, he called a retreat, as he was not prepared to fight four Spinjitzu masters. Garmadon then gave Samukai new orders: Let the Ninja think they're winning. Samukai continued to seek the Golden Weapons, but allowed the Ninja to dominate until just before they began to search for the Sword of Fire. Then, Garmadon's scheme came into play. Kai was lured away from the rest of the group, and Sensei Wu followed. Samukai and his army then ambushed Jay, Zane and Cole, claiming the Shurikens of Ice, the Scythe of Quakes, and the Nunchucks of Lightning for Garmadon.

Betrayal To Lord Garmadon
Garmadon then sent him back to the Underworld, where he fought Sensei Wu, who was wielding the Sword of Fire. Samukai defeated him, and took up the Sword, intending to use the Four Weapons and their power to defeat Garmadon and regain control of the Underworld. However, the power of the Four Weapons united was too much for anyone to handle, and as a result, Samukai disintegrates and a Portal through space and time appears, which was Garmadon's true plan all along. Having succeeded in his plan, Garmadon then escapes through the Portal vowing to return with more power so that he can wield the Four Weapons and recreate Ninjago in his own image.

Appearance
Samukai had four arms and a large head. He also had two scars above his eyes, and wore the standard chest plate of a fire-based General of the Skeleton Army. He once wore the helmet Lord Garmadon wore in 2011, as it seems this helmet goes to the ruler of the Underworld.

Weapons
Samukai used four Bone Daggers. He also attempted to use all four Golden Weapons at once and as a result was destroyed by them, because no one can wield all four at once, with the exception of the First Spinjitzu Master and later, Lord Garmadon.

Trivia

 * Samukai's name is a pun on of the word "Samurai."
 * Samukai is the only Skulkin that doesn't have a spinner/Character Card. It may be caused by the fact that he is pretty large and heavy for a minifigure and his spinner wouldn't be balanced well enough to work properly.