DM plot twist help.

[Shadowbane13]

Hey I’m currently running a campaign and my group is working with an NPC to do some semi important tasks relevant to the storyline. My thing is I was going to have the NPC be like possessed or maybe an evil creature in disguise. Anyone got any good ideas as far as what would be a good enemy that possessed someone? I was thinking of putting a devil in the human body and he emerges at the dramatic climax. But not sure how well that’ll go.

[Fire Tarrasque]

I mean, what's the rest of the plot? Is it Devil-centric? What will their level be?
Otherwise, Oblex. They were only recently released, and are already gaining notoriety.

[MoiMagnus]

Some advice:

1) Go to the spell section, look at all the diviniation-like spells, and for each spell, makes sure you have a way to make your great villain not being busted. If you have to improvise a solution, the players will feel like you cheated on at the revelation moment
(What is the point of circle of truth if it can't detect that kind of betrayal? If you didn't made clear beforehand that there is way to go around divination, it will feel inconsistent).
You have to know what does the gods know about him, what kind of mental protection he has, ...

2) Something that work reasonably well is to make this character be quite important at the beginning, but once the PJ have a high enough level to detect that he is the bad guy, they no longer meet him in person (he is far away to do something and communicate trough letters, trough a loyal friend, ...)

3) Make sure that the PCs are more than just puppets following order until betrayal of the bad guy. If the only relevant things of your campaign is this NPC, it will be absolutely obvious to everyone that this NPC will either die either betray at the critical moment. "Disney bad guys" are interesting bad guys for film and stories, but take to much place in the plot for a D&D campaign. It is important for the players to feel like the conclusion would have been different if they had made different choices.

So don't take the stereotypical "NPC recruit PCs for an important task, but in fact it was a trap and NPC betray, but NPC underestimated PCs so PCs still win at the end". In this scenario, every relevant choice is made by the NPC, the PCs just follow their fate passively and win because the NPC was too stupid/arrogant/...

A better way with approximately the same scenario is "PCs have a problem and manage to obtain the help from NPC, by their choices (helping someone, investigating a murder, ...) the PCs will progressively start posing problems to the plans of NPC, so NPC will first try to discretely get rid of the PCs, and when confronted about by the PCs, he will openly betray them."

4) Instead of possession, you can also just take someone under a magically binding contract with a devil. Shapeshifter may also work.

[Mercurias]

Make him possessed by the vengeful ghost of a murder victim. Your players will be steered into avenging his murder or otherwise doing awful things to the people who killed him until they catch on and play ghostbusters.

[Vogie]

The actual BBEG could be a GOO chain warlock. When the party finds the person, they are actually just an enthralled lackey, and the familiar was actually the BBEG's familiar, who was watching over the whole thing.

[EvilAnagram]

I've had nothing but success with Rakshasas in this regard.

[Shadowbane13]

I actually came up with an idea, not necessarily possession but instead it’s a fallen angel aspect. The angel was banished as per usual and has been trying to regain the trust and honor of his/her god/goddess who banished them by committing tyrannical acts against the communities. He’s hidden as a humanoid for the time being and is attempting to recruit the PCs to help him do these acts to work his way back to the heavens of some sort. I’m still working out details about it and the deities exactly but it may be good. Either that or I’m gonna go with the idea of a vengeful possession of a sort.

[Cynthaer]

I was thinking of putting a devil in the human body and he emerges at the dramatic climax. But not sure how well that’ll go.


1) Go to the spell section, look at all the diviniation-like spells, and for each spell, makes sure you have a way to make your great villain not being busted. If you have to improvise a solution, the players will feel like you cheated on at the revelation moment
(What is the point of circle of truth if it can't detect that kind of betrayal? If you didn't made clear beforehand that there is way to go around divination, it will feel inconsistent).
You have to know what does the gods know about him, what kind of mental protection he has, ...

I don't outright disagree, but I'm reminded of something Mike Mearls said in some video.

Basically, he argues that outright twists (keeping something completely hidden and then revealing it to shake up the story) are better suited for a straightforward storytelling medium, like books or movies. The equivalent moment of coolness for a game like D&D, he says, is when the players figure out something.

I don't think it's a hard and fast rule, like you should never spring a sudden twist on the players, but I do think there's a lot of value in approaching your story with the expectation that the players will figure it out at some point, and whenever that realization starts to dawn on them, it's going to be awesome.

In this case, I think it's worth considering the ways your players might uncover the villain "early", but your goal isn't necessarily to ensure they can't succeed. Rather, assume the players will realize the betrayal at some point, consider what will happen when they do, and if nobody figures it out before point X then he emerges during the climax.

It's a more robust approach than relying on the players not learning something.

EDIT: I think the rest of MoiMagnus's post is solid enough, for the record. :)