Slugterra - Season 4 Episode 1 Into the Shadows: Back on the Shane Gang (1) Slug it out!
Overview: As the Shane Gang returns to the 99 caverns from their Eastern adventure, they find Gateway Cavern overrun with slugs. In the Shane Gang's absence, the Shadow Clan took a different approach to protecting the caverns, putting slugs before the needs of people and it's up to Eli and the gang to restore balance.