Ghoul from Beyond (S02E01)

Just as Eli Shane believes he's finally put an end to the wicked Dr. Blakk, a fresh threat arises from beyond the 99 caverns. The Shane Gang quickly springs into action, but they're unprepared for the astonishing discovery that awaits them: a slug exhibiting abilities never witnessed—or heard—before in Slugterra! With conventional slugslinging techniques rendered useless, Eli must enter a completely new kind of showdown to protect Slugterra and ensure his own survival.