Eli has added some awesome new slugs to his arsenal: the Elementals. But the Elemental Slugs are ancient, extremely powerful, and temperamental, and Eli can’t control them. Junjie, the newest member of the Shane Gang, has the solution: Eli must learn SLUG FU, the ancient form of slugslinging that Junjie mastered in the Eastern Caverns. Slug Fu is the art of guiding and controlling a slug in battle—a skill that only the greatest slugslingers can master. But while Eli and Junjie train in isolation, separated from the Shane Gang and all of Eli’s slugs, a mysterious new villain named Spirex unleashes an evil plan that will rock Slugterra to its core! All he needs to complete his plan are the Elemental Slugs. Luckily, they’re safe with the Shane Gang…or would be, if Pronto hadn’t annoyed them so much that they ran away. As Kord, Trixie and Pronto struggle to keep the wily Elementals out of the wrong hands, Eli and Junjie engage in a showdown with Spirex before he can reduce the 99 caverns to rubble!