D&D 5E Persuade, Intimidate, and Deceive used vs. PCs

[Maxperson]

First, I wouldn't use an adventure module as proof of anything about the actual rules of the game, especially modules that were written early on in the design process.

Leaving that aside, the doppelganger can try to deceive the PCs. It just tells the lies and then it's on the players to declare an action along the lines of wanting to determine the doppelganger's truthfulness (or agenda or personal characteristics). At that point, the DM can - if he or she finds the player's stated action to have an uncertain outcome and a meaningful consequence of failure - use the doppelganger's Charisma (Deception) check to set the DC for the PC's Wisdom (Insight) check. If the PC succeeds, then the narrated result can be that the doppelganger is not being truthful. If the PC fails, then the narrated result can be that the PC can't tell if it's being truthful or not. In either case, it's up to the player how the character responds.

You could also give the PC disadvantage, since the doppleganger is supposed to have advantage. Just switch it around so it's the PC making the check, but it's a very difficult check.

 

[iserith]

You could also give the PC disadvantage, since the doppleganger is supposed to have advantage. Just switch it around so it's the PC making the check, but it's a very difficult check.

I probably wouldn't go that route, but I wouldn't be offended as a player if a DM ruled that way.

 

[c0wfunk]

2) Another approach is to actually try to deceive/persuade the players. ...
...
The moral of the story is: DON'T HELP DEMONS COMPLETE RITUALS.

Sheesh.

So I went with this, and in fact we had a pretty good scene, my bbeg convinced them to help him open the portal. Once open, the party got antsy and a fight broke out wherein they defeated the bad guy but the portal remained open. Our hexblade, eager to meet his patron, dove into the portal enthusiastically while the rest of the party looked on with a “uhhh nope” and there we left it. One roll came out of the scene and it was on whether the cleric, onlooking skeptically, saw through the doppelgänger’s act, and she did not. Nevertheless she remained skeptical. I never did have to roll persuasion or use mass suggestion or kidnap the players and yet the portal is open and now I have to figure how to get the warlock back or the party in

It feels like with 3/4 not wanting to go I should honor that, give the warlock a quick scene with his patron -they also leveled up to 5 so I may do some training or challenge with him - then get him back to the material plane. Rather than somehow forcing the rest of the party into the portal they made it clear they did not want to enter. They’re all creeped out by the warlock enough that they aren’t going to go just to help him.

Thanks for the tips, this thread was really helpful in my navigation of this scene.