I've had this thought for a while now. An idea that has been brewing in my head for quite some time and I have shared bits of here and there. I want to theorize about what may happen in The Rise of Skywalker. Or, more specifically, what Sidious' ultimate goal may be.

Although the way I'm going to treat this theory is less of a "this is what I'm sure is going to happen" and more of a "how cool would it be if this happened?".

First off, throughout the Skywalker Saga, what has Sidious been after? And how has he tried to attain it?
Immortality? Galactic Rule? Power for power's sake? The continuation of Sith dominion?

Well, he wants all of these, sure.
But I also think that these are means for a much greater end. He wants to become essentially a god. He wants to become the physical(?) manifestation of the Dark Side, with absolute control over the universe. He wants to BECOME the Dark Side.

To rule the Galaxy as its Emperor is impressive, but it's also a matter of mundane and material dominance. Not Cosmic or absolute.

To achieve immortality is one thing, but it's also a narrow view of what can be achieved through our body's crude matter. It's also a path that leaves you as flesh and bone, immortal and timeless, but likely still able to be slain. It takes only one mistake. No matter the power.

And the Sith are an idea, a name that inspires fear and hate from their enemies, but at the core of their doctrine is the self. The Force shall free ME. Sidious IS the Sith. And so his dominion is that of the Sith. He has no plans of passing the torch.

Sidious is stagnation. Sidious is death. Sidious is the end.

Of course it's not unheard of for Sith, or powerful Dark Side users in general, to manifest themselves after death. But each time we've seen it, they've been something… Less. A shadow of their former selves. Trapped either by their inability or their unwillingness to move on.

Having lost most of their power and remaining as barely a whisper in living ears. Tormented by isolation, by having lost everything they ever held dear, or by straight up pain.

We've seen dark spirits haunting ruins, corrupting artifacts or masks and affecting the real world in small ways, but they cannot escape, not truly. Or even if they do, whatever influence they have on the material world is minimal or short lived.

This isn't true immortality. This is a prison, an anchor that stops them from moving on. Often self-made. So how does one achieve True Immortality?

Well, there is only one path to True Immortality in Star Wars. Only one way to transcend and become one with the Force, while also retaining the sense of self.
I believe that Sidious is looking to take over and corrupt the most sacred of lessons a Force user could ever learn.

To let go of his physical self and become not only immortal, but eternal and incorporeal. To become an all seeing, all powerful manifestation of the Dark. To shape reality to his vision.

Becoming a Force Ghost is not quite as simple as just projecting yourself from beyond death. Those who have achieved this state have become one with the Force, but retain their consciousness. They are connected to it in a way that no other living being is.

They are directly connected to the Living and Cosmic Force, because they are a part of it. Force Ghosts are essentially what life is, beneath it all, once we let go of the material that we find ourselves in.
"Luminous beings are we. Not this crude matter."

But with them being a part of this great Cosmic energy, they are also well aware of their purpose, of their potential power and of why they need to restrain themselves. They act as mentors, guides, beacons for the next generation to learn from and move past them.

This is their story, and it would do no good for them to not face their challenges and become better for it.
This is their story, and it would do no good for them to not face their challenges and become better for it.

But imagine if someone could achieve this state of being, but without the limitations in morality. They would have no limit to what power they could wield, as they are a direct part of the Force.

With that direct connection to the wellspring that is the Force, it could potentially break the very fabric of the universe. He would be a Force God akin to or maybe even more powerful than the Ones from Mortis.

And the other Force Ghosts trying to stop him with their power would only shatter the Galaxy and the Force even more. Which is why they need the heroes of this trilogy.

But it's not quite as easy as learning a secret in an old tome and performing a ritual. There are rules to this.
It's a technique that must be taught. Something that you must learn to be able to achieve. It doesn't just happen with any powerful Light Side user when they die.

It's a rare thing, only rediscovered recently by Qui-gon, learning from a Shaman of the Whills, and Yoda learning from the Force Priestesses at the Wellspring of Life, and later from Qui-gon.
To become a Force Ghost, one need to have achieved a sort of enlightenment.

You cannot become a Force Ghost without an absolute commitment to compassion, selflessness and love. This isn't something that can be tricked. It simply is true or it isn't.
Which is why Sidious is going to need Rey, I believe.

I've become convinced that Sidious is done with the Skywalkers. He wants nothing to do with Ben, but Rey has something he needs/wants.

There are so many great theories out there surrounding Rey. But one that has been in people's minds for a while (especially Reylos) has been the idea that at some point Rey may resurrect Ben Solo after some heroic sacrifice.

What if this ability is exactly what Sidious wants with Rey? Maybe he needs her to bring life into his trapped spirit (which would result in her death, of which she's unaware), but he somehow interrupts the process halfway, takes advantage of Rey's compassionate nature,

and twists the Force into giving him the gift that was meant for Rey? (maybe he used the excuse of bringing back her parents to trick her?)

Or maybe he promises a place at his side, a way for her to end all suffering in the Galaxy through that power? All she needs to do is accept death

(I get the feeling that whatever Sidious offers Rey is going to involve her death in some way. Knowingly or unknowingly. Which in turn means that her choosing to fight him later on with Ben Solo is her choosing life over death).

It's possible that Rey and Kylo release Sidious accidentally from wherever he's been trapped since his death, but he remains weak and that this offer occurs after the release. Or maybe the offer IS how he's released in the first place. Not sure. Leaning towards the former.

Admittedly, the specifics of how he intends to use Rey aren't the most solid here, but they're also not the most important part.

The point is, he needs her, and through her, he may be able to achieve something no other Sith has ever been able to do. Because no other Sith had Rey. Not just True Immortality. Unlimited Power on a Cosmic level.

"Darkness rises, and light to meet it."
But he will fail in the end. Because Rey is not alone. Because she is one half of the protagonist and the other half will Rise. This is a big part of why I think Ben Solo's redemption is key to this movie.

Not just for its own sake, but because he will be the knight chosen by the Jedi Force Ghosts to aid Rey in challenging the greatest threat the Galaxy has seen.

Ben and Rey will unite, and will finally vanquish the evil entity that is Sidious, while also finding balance within and between themselves, with the blessing and maybe aid of the Masters. Past and future will split and combine. They will finish what Anakin Skywalker started.

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