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.
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 [S5E1] Mort Dinner Rick Andre
In the end, Morty saves Jessica, but the experience has changed her. Having spent what felt like eons frozen in a time-stasis crystal in the other dimension, she has transcended human emotion. She tells Morty she just wants to be friends because she is now a "Time God." Morty enters the dimension to save her, and
The episode ends with Rick getting arrested by the literal police (controlled by Nimbus), and Morty sitting on the roof, realizing that his desperate attempt to have a normal night resulted in the destruction of an entire civilization and his chances with his crush. Morty just wants his date with Jessica to
They are a medieval society dedicated to killing him.
This turns out to be a massive mistake. By touching the ocean, Rick has broken an ancient treaty with his flamboyant, sea-dwelling nemesis: , the King of the Ocean. The Dinner Party from Hell
They have steampunk technology and "Wine-Guardians."