Eli has added some awesome new slugs to his arsenal: the Elementals. But the Elemental Slugs are ancient, extremely powerful, and temperamental, and Eli cant control them. Junjie, the newest member of the Shane Gang, has the solution: Eli must learn Slug Fu, the ancient and mysterious form of slug-slinging that Junjie mastered when he lived in the Eastern Caverns. The Slug Fu training wont be easy, and its something Eli and Junjie must do alone. That means leaving Kord, Trixie and Pronto behindand all of Elis slugs, too! So things get even tougher when Elis training is cut short by a mysterious new villain with a seriously insane plan to rock Slugterra to its core. The villain needs only one thing to unleash his evil plan: the Elemental Slugs! Luckily, Eli left them with the rest of the Shane Gang, so they are safe. Or they would be, if Pronto hadnt annoyed them so much that they hopped off and 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 the madman before he can reduce the 99 caverns to rubble!