You were just wondering about that, weren’t you? Well, I’ll explain.
Every big epic in fantasy or science fiction, needs a legendary villain-character like Darth Vader, Gollum or Agent Smith. But these three are not normal evil doers. They are very special, because their destiny is directly tied to the resolution of the whole story. They are more like causal agents than just ordinary bad guys.
Their evil is also much more nuanced than the other main villains in their holy trilogies. And their motivations are often harder to fully grasp. Take emperor Palpatine in Star Wars. He is just evil to the core. There is not a single shade of grey: he is BAD. Darth Vader, on the other hand, was actually a good man before he was seduced by the dark side of the force. Luckily, for the oppressed galaxy, Vader’s son Luke Skywalker felt there was still good in him. Luke exploited this inner conflict, which lead to the death of Palpatine by Vader’s hand at the end of Return of the Jedi. The galaxy was free once again due to Vader’s destiny.
Gollum and Agent Smith (especially after his supposed destruction by Neo in the first Matrix movie) don’t even belong to the villain class and are free agents, so to speak, Smith quite literally. They are just roaming around in their fantasy worlds, driven by their own insatiable desires. Gollum by his addiction to the Ring of Power, and Smith by his need to destroy his arch enemy Neo and the entire simulated computerworld the Matrix with it. But, like in Vader’s case, through their actions they enable the heroes of their stories to fulfill their appointed tasks while they would have otherwise failed.
Like Frodo in The Lord of the Rings. He managed to get the ring all the way to Mount Doom, but could unavoidably no longer resist the power of the mighty precious and thus refused to destroy it. Gollum took his chance and jumped at Frodo, bit off his finger, and took the ring. But he could only enjoy it for a brief moment. As a crazed Frodo attacked him, Gollum fell to his doom taking the ring with him. The panic in Sauron’s one eye is very satisfying. His reign is over forever. Gandalf had foreseen this turn of events: ‘My heart tells me that Gollum has some part to play yet, for good or ill, before this is over.’
Agent Smith’s faith is similar. When Neo realises that it is inevitable that Smith – who he has destroyed before – must now destroy him in order for things to end. He allows Smith to clone him, like he has done to the entire population of the Matrix (‘me, me, me’). But since Neo is the One, the anomaly of the system, this creates a fatal chain reaction eliminating the virus Smith. By pursuing his own purposes, against the will of his masters (the machines in case of The Matrix), he ensures that the humans are set free.
Do all epics have this type of causal agent? What about Harry Potter for example? Well in a way: yes, a very interesting one. When Voldemort tried to kill Harry when he was a baby, he unwillingly put a horcrux (a piece of his soul) in Harry. While Harry was growing up, he slowly discovered his connection to the Dark Lord. In the end, the only way to defeat him, was by letting Voldemort kill him. This villain created a causal agent himself that lead to his doom! Because Voldemort didn’t kill Harry, but just the horcrux. The now released Harry could return and finish off Voldemort in a final confrontation, ridding the wizard and muggle world of this ultimate baddie.
The world is more complex than just good-evil. While most of the characters in these epics are either of the hero or villain archetype, these causal agents are not so easily defined. So to answer the question, what do they have in common? They are tools used by the clashing higher forces to decide the faith of the world. Apparently, free will is absent in these worlds, and we are merely instruments of the ruling powers. This makes sense, for at least two of these trilogies (Star Wars and The Matrix) are inspired by Eastern Philosophy of which some movements (Advaita Vedanta) teaches us that free will is an illusion. The Lord of the Rings seems more in tune with paganism that also suggests that greater spiritual forces can impact the course of events or the ultimate outcome.
The individual destinies of these characters are thus intertwined with the destiny of the world at large. Thereby, they completely transcend a clearcut character definition. Beneath their wicked appearances, they actually become saviors, even though that was never their intention. Gandalf nailed it when he said: ‘Even the very wise cannot see all ends.’ Good, bad, everyone has their own perspective. But in the end, love and goodness will always be victorious.