WARNING: The following contains spoilers for Rick and Morty Season 5, Episode 10, "Rickmurai Jack."
Evil Morty, first introduced in the Season 1 episode "Close Rick-counters of the Rick Kind," has become one of Rick and Morty's fan-favorite villains despite his limited number of appearances. The Season 5 finale, "Rickmurai Jack," puts the spotlight on Evil Morty for the first time since Season 3's "The Ricklantis Mixup," and finally offers some explanation for why the Citadel's first Morty president has been killing Ricks and torturing other Morties.
But in explaining why he is "evil," the villainous Morty suddenly becomes sympathetic.
Evil Morty's ultimate goal is to escape the Central Finite Curve, a concept first mentioned by the Council of Ricks in "Close Rick-counters" but only now has it been explained. The Central Finite Curve locks off every universe in which Rick is the smartest person from the rest of the multiverse. Evil Morty wants out from the whole system of the Ricks' abuse. "That's what makes me evil," he says, "being sick of him. If you've ever been sick of him, you've been evil too." These "evil" motives are surprisingly sympathetic, and considering how Ricks killing each other is just commonly accepted, it's hard to truly say Evil Morty's actions are really worse than the system around him.
"Rickmurai Jack" disproves the popular fan theories that Season 5 was going to involve the series' main C-137 Morty becoming Evil Morty. President Morty does make the main Morty an offer to leave his Rick and become "evil" as well, but even with his increased understanding of Rick's toxicity, he still can't bring himself to abandon his grandpa. Rick himself is surprised and wonders if Morties in general are brought up to be too forgiving of his failings.
By the end of the episode, Evil Morty achieves his goal. Using the blood of slaughtered Operation Phoenix clones, he tears a rip in the Central Finite Curve which he flies through in his spaceship. Breaking through to the other side, he shoots a portal gun, this one making gold portals instead of Rick's standard green ones. The C-137 Rick and Morty mitigate some of the destruction Evil Morty caused to the Citadel by detaching one module and evacuating as many other Morties as possible, but this is the end of an era -- Evil Morty leaves the Curve with a ridiculously high body count.
Where does Rick and Morty go from here? Much of the season finale's meta dialogue acknowledged how reluctant Dan Harmon and Justin Roiland have been to tell serialized stories, and by destroying the Citadel and sending Evil Morty to another universe, "Rickmurai Jack" could be seen as closing the book on further lore in these areas. A return to the typical status quo, however, doesn't seem possible either. In his destruction of the Citadel, Evil Morty depleted all the portal fluid, so Rick's most powerful tool is unusable for now. Beings smarter than Rick now have a gateway through which they can enter this universe, and confronting Evil Morty is an event neither Rick nor Morty will be able to just shake off as if nothing happened.
All episodes of Rick and Morty Season 5 are now streaming on Adult Swim's website.