In a magical yet terrifying North Pole, the reindeer face an unprecedented challenge as the naughty list goes missing just before Christmas. Dasher, Vixen, Blitzen, Cupid, and Dancer split into teams to search for it, but their efforts yield no results. Santa, growing anxious, encourages them to keep looking. When Prancer finds a mysterious key that belongs to Santa's old office, the team rushes there only to uncover not just the ancient naughty list but also a hidden updated list. As they work to unravel the mystery of the hidden lists, a gnome attempting to sabotage Santa's sleigh is captured. He reveals that someone is intent on ruining Christmas. Suddenly, chaos erupts as Krampus, Santa's dark counterpart, orchestrates an attack on the workshop, leading to a fierce battle between the reindeer and Krampus's minions, including wolves and shadowy figures.