They have steampunk technology and "Wine-Guardians."
Morty enters the dimension to save her, and Rick eventually joins the fight after his dinner with Nimbus falls apart. Just as they are about to be overwhelmed by the futuristic tech of the "Narnia" world, Mr. Nimbus saves the day by controlling the water (and the police) to bail them out. [S5E1] Mort Dinner Rick Andre
Morty just wants his date with Jessica to go well, but he ends up accidentally genociding an entire timeline just to keep the wine flowing. Eventually, the portal-dwellers kidnap Jessica, pulling her into their world. The Conclusion They have steampunk technology and "Wine-Guardians