So the idea is that the villains are this dark side cult, on fringes of galaxy, planning a secret war to usurp Palpatine, and they're led by this mistress who is immensely powerful in the force, able to use all the typical abilities, but the kicker is decades ago as a Jedi she stumbled upon an ancient force technique that allows her to prolong her life by leeching off the "essence" of others. (She's vampiric in a way, the stronger a force sensitive is the more longevity she can suck out of them). This has led her to be old enough to remember decades before the clone wars and yet still look youthful and vibrant though evil to the core. With the PCs she would see them as potential servants or essence food, and bring them to her secret planet where they would escape and lead her on a desperate chase to kill them before they can get word of her secret out to the galaxy.

Does this seem far fetched? I like my campaigns to be as believable as possible, and with this woman's ability I feel like I might be stretching it, what do you all think?

Constructive criticism and story progression ideas are welcome, I could use all the help I could get.

It sounds plausible to me. In fact, her backstory is somewhat similar to Darth Zash . Only Zash was transferring her consciousness to other.

So I guess not very similar at all.

You can make her powerful, but know that messing with Palpatine is not a good idea. Make her absolutely terrifying, but do some sort of scene showing she is an ANT by comparison to the Emperor. However, the idea of absorbing the life essence is perfectly fine. As a matter of fact, Palpatine wanted to do that eventually. (Albeit he wanted to eventually "eat" planets, stars, and even the entire galaxy. And then the rest of the universe.)

See also, Vitiate.

He and Palpatine have much in common once you get into EU / Legends material... immensely evil to the point of caricature, wanting to "eat" all life in the galaxy, keep coming back from being "destroyed", etc.

They're the two biggest Villain Sues of the setting (and I don't call things "Sue" lightly at all, is a grossly misused and overused term.)

I was about to mention Vitiate, but was beaten to the punch!

I recommend reading and watching up on that particular character from the KOTOR MMO as there quite a few ideas there that might inspire your campaign!

I recall Vitiate performed a ritual that completely wiped out all life on a world, like Zash he possessed others including force sensitive including a Jedi Master to function as his Horcrux let alone what's going on currently in the MMO which I'm not even going to explain!

You might want to take a note about the other darksider cult shown in the Clone Wars series that effectively involved Darth Maul's origin needless to say that's quite the anthill you just kicked over!!!

Thanks everyone, this is definitely helping flesh this lady out. Now I wasn't exactly planning on Palpatine or Vader showing up in the campaign at all, as I wanted the PCs to eventually get to a point strong enough in their abilities to fight as one and eventually defeat her. How would I show she's nothing compared to Palpatine without him showing up? Or should he?

I was about to mention Vitiate, but was beaten to the punch!

I recommend reading and watching up on that particular character from the KOTOR MMO as there quite a few ideas there that might inspire your campaign!

I recall Vitiate performed a ritual that completely wiped out all life on a world, like Zash he possessed others including force sensitive including a Jedi Master to function as his Horcrux let alone what's going on currently in the MMO which I'm not even going to explain!

You might want to take a note about the other darksider cult shown in the Clone Wars series that effectively involved Darth Maul's origin needless to say that's quite the anthill you just kicked over!!!

The Nightsisters .

I think people have built their reverence of Vader and Palpatine's power into a dogma of invincibility. I think their myth is bigger than they are. They are very impressive and should be tough nuts to crack, but should not be viewed as infallible, omniscient, or omnipotent. In fact, they were taken down by a greenhorn Jedi. You can interpret that as destiny and cast Luke as a sort of space messiah who redeems the space messiah. Or, you can look at it with a hard eye and ask: "what do I actually see them do?"

OT Vader:

1. He lifts people with one arm easily. Brawn-4 plus Enhance. But, in the OT, he never gets "leapy." He's probably deep in the athletics, brawn, brawl side of the tree.
2. He senses "presences," feelings, and emotions. That's the basic sense power with one control upgrade. However, he often does so at great range. So, he probably has several range upgrades.
3. He force chokes people. You can do that with basic bind and a dark side pip.
4. Vader is to cool under pressure to bother blocking blaster bolts with a saber. He has Imperial Valor (minions get shot) and the one time a protagonists sends a blaster bolt his way, he absorbs it. That could be a deep buy into the Protect tree, or it could be his extra-special sith-armor, or even just the result of the setback dice armor can provide.
5. He throws a bunch of boxes and things at luke, pulling some out of their fastenings. He also pulls Han's blaster out of his hand. That is Move with at least three control upgrades, two strength upgrades, and depending on how you interpret the objects flying at Luke in terms of rounds from 0 to 4 magnitude upgrades.
6. He's able to drive luke where he wants him in a duel, which is drive back.
7. He's able to integrate force powers into his fighting style, which some talents make possible (incl. in niman).
8. He scares people senseless - intimidate, fearsome, terrify, imp. terrify.
9. He's a crazy good starfighter pilot.
10. He's a very dangerous swordsman.

All of that is scary, but its not godlike, and while you can build him as an unstoppable force of nature, he's really not when you consider the opposition we see him face. A wily smuggler, a spitfire princess, and a farm boy turned rebel turned entry level Jedi Knight. Vader isn't stupid. He chooses the ground and controls the terms of engagement, which is something he learned the hard way. A younger Obi-Wan utterly defeated him when he was, theoretically, more powerful. And, older Obi-Wan surrendered to death and let Vader kill him. He was holding his own prior to that. In my opinion, a skilled Jedi Knight or Master would give Vader a run for his money - its just, there aren't any left to face him. Its valid, IMO, to think his myth and propaganda are better than he is.

If I were to build Vader using PC rules, I'd give him Force Rating-4, Brawn-4, Lightsaber-4, and the full Aggressor, Starfighter Ace, and Shii-Cho trees. I'd also add most of the Makashi Duelist or Niman Disciple Tree (one or the other). I'd also slap on Drive Back and Imperial Valor. Powers, pretty much as laid out above. And that's all. If he faces multiple opponents, esp. multiple force users with laser swords, I'll give him an extra action. If he's one on one, not. However, the real trick to running him isn't amping his personal power. Vader controls the terms of engagement. He only took on Luke mano-a-mano when he had complete control of the ground. He only walks headlong into enemy forces when he has overwhelming power, like the 501st Legion, in his wake.

OT Palpy:

1. "The Emperor has foreseen it!" He probably has the whole foresee tree.
2. He's very aware of people's emotions and the currents of the Force. He probably has the whole sense tree.
3. He uses Force Lightning. That's harm or unleash. A lot of it.
4. He knows a bunch of ambiguously referenced Sith secrets. Sith Alchemy of some sort.
5. He's got cunning coming out of his unmentionables. 6.

But, in the OT, there is nothing to suggest he's invincible. He's just a spooky dark-side prophet who throws lightning bolts. Now, in the prequels we do see him use massive amounts of move that indicate he has the whole tree. Despite this, Yoda almost takes him and its more bad luck that he doesn't than not. Also, considering how diminished he is physically after Windu beats him (only Anakin's intervention saves him), he might not be up to fight with multiple opponents anymore.. Its entirely up to the viewer to decide for themselves whether is still up to dominating in a saber fight. I think it doesn't fit and actually reduces the gravitas he had in the OT.

In other words, I don't think its at all necessary to show your baddy is an "ant" compared to the Emperor.

Unless, of course, you have graven images of Vader and Palpatine in your home.

Completely agree, regarding the way that Palpatine and Vadar have been mythologized.

As a matter of fact, Palpatine wanted to do that eventually. (Albeit he wanted to eventually "eat" planets, stars, and even the entire galaxy. And then the rest of the universe.)

The what? Is that Legends or canon? Source?

I'm totally stealing those Vader specs in case my PCs ever get unruly. In the idea in my head, though, this mistress thats wants to usurp them has been alive as long if not longer than Palpatine himself with all the essence stealing and is still youthful. She would be a very powerful adversary, and in the ideas of character specs for her it looks like she could hold her own against Vader and Palpatine, but just maybe need some help from allies to overcome them. I never planned on this happening though, as the PCs would run into her and bring her down before she led her crusade far enough to Coruscant. Do you think a duel between the Sith and the mistress should happen for storytelling? Yeah or nay?

I'm totally stealing those Vader specs in case my PCs ever get unruly. In the idea in my head, though, this mistress thats wants to usurp them has been alive as long if not longer than Palpatine himself with all the essence stealing and is still youthful. She would be a very powerful adversary, and in the ideas of character specs for her it looks like she could hold her own against Vader and Palpatine, but just maybe need some help from allies to overcome them. I never planned on this happening though, as the PCs would run into her and bring her down before she led her crusade far enough to Coruscant. Do you think a duel between the Sith and the mistress should happen for storytelling? Yeah or nay?

Palpatine was born 84 years before the Battle of Yavin, if that helps set a timeframe for comparison.