Ghost Story (Flashback)
Several years later, the Grundle species would eventually go extinct, under unknown circumstances.
Lord Garmadon attempted to resurrect the Grundle with the power of the Mega Weapon, seeking to use it as the ultimate anti-Ninja weapon. The Ninja interfered with the ritual, causing them to be reverted to children—unfortunately for them, the Grundle was still revived and began stalking the city in search of its prey.
With their fighting skills reduced with their age, the Ninja were helpless against the Grundle, but Lloyd took them to Rufus MacAllister's comic book store, where he felt that they could find some defense against the beast. Using light-up illuma-swords, the Ninja were able to keep the Grundle at bay for a time, but the prehistoric monster eventually knocked the weapons from their hands.
The Ninja were only saved by the arrival of Nya and Sensei Wu, who had brought age-increasing Tomorrow's Tea with them. Despite being in range of the tea's effect, Lloyd threw the tea at the Grundle, undoing the time-reversal spell that had revived it and de-aged the Ninja. The Grundle collapsed into a pile of bones once again, and the Ninja were restored to their former selves - along with Lloyd, who was now a teenager.
A statue of the Grundle was part of the Ninja exhibit at the museum.
A green version of the Grundle is seen chasing Lloyd and Harumi.
Abilities and Attributes
The Grundle is fast, powerful, and resilient, having a hide immune to ordinary weapons. However, it is a nocturnal creature, and thus very vulnerable to light - even the relatively meager light projected by toy illuma-swords is enough to make it flinch.
Its claws can tear through metal and its senses are keen enough to track even a Ninja. It constantly secretes large amounts of viscous green ooze from its mouth—presumably some type of poison—but its effects are unknown.
- It resembles a large theropod dinosaur such as Giganotosaurus or Tyrannosaurus, rather than a dromaeosaurid.
- A model of a Grundle was on display in the Ninja exhibit at the Museum of History.
- As seen in "Ghost Story," Grundles were still alive during the era of the Serpentine War, but went extinct sometime afterwards.
- In the episode "The Quiet One," when the episode begins, Lloyd and Harumi are seen being chased by a Grundle (only this time in green). While the Grundle chases both of them, they both fall into a hole. The Grundle then could not get to them and it walked away. This could mean that some sort of Grundle species is still alive.