> Think about how you as a DM resolve non-combat conflicts in D&D - I want to persude the King's council to do this
If your players are anything like my players, they'll cast Dominate Person on the King's Council. I'll have to note with them that the King's Council are elite and therefore expected to have Mind Blank, offering them immunity to their attempts.
They can work with persuasion, but if they are under the effect of Glibness, the King's Wizard would be able to see Glibness as an aura. The King's Paladin may use Zone of Truth to counteract the effects of Glibness, or maybe point out Glibness as "cheating" in the King's Court.
(Mind Blank doesn't help vs Glibness. Glibness simply makes the party's Bard's lies more believable. Its not an actual enchantment upon the King's Court, but instead a "buff" given to the Bard. So additional levels of security for the King's Guard are needed.)
As such, the battle of spells, trust, and other such interactions becomes a game. How well have the players prepared for the social encounter? Are they trying to use spells to "cheat"? How are the king's guards, Wizards, and Clerics trying to prevent the cheating?
Should I let the players get away with cheating? Well, I don't decide. I let the dice decide. As well as the rules that the game are around.
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Maybe the party is able to successfully hide the Glibness through some means. If they thought through their attempts to +40 Bluff check to convince the King's court of their intentions, I will grant them the +40 bluff check.
But if their Glibness / attempts at cheating are discovered, I'll grant a heavy penalty (-15) to their interactions for the rest of court.
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Players _WILL_ attempt to cheat (aka: use a spell to "solve") social encounters. This is just part of the game, and part of the fun. Are you, the dungeon master, ready to offer them a proper game of wits and preparation?
> OK so why bother having specific named spells with specific mechanics? Just say that guy's a level 7 wizard so his spell has strength 7+d6, my guy's a level 3 wizard so my spell has strength 3+d6, we make our rolls and the explanation of what happens (he bewitches my mate to make him insane and I try to dispel it) is purely flavour? That's no less objective, no less easy to be fair about (in fact it gives me far fewer avenues to try and bullshit you), but it doesn't require us to go memorize a textbook's worth of spell names and interactions.
Notice the above interactions. Glibness, despite level 3, avoids the Mind Blank preparation. Mind Blank does protect vs the more direct forms of enchantment (ex: Suggestion, Dominate Person, Geass), but it isn't a complete defense for the King's guard.
Of course, maybe the King's Dragon simply casts Anti-magic field and negates all magical preparations for the encountrer.
Note that Artifacts (aka: items from god) are immune vs mortal magic, and are one able to avoid the effects of Anti-magic field. This is where the DM has an opportunity to override the rules of the system and provide a story. (You can, at any time, "win the bullshit" fest by declaring an item a special artifact).
But you want to ensure that if you ever do declare a god-level artifact in play, that the players "saw it coming" to an extent (foreshadowing), or otherwise works in your story.
This is far more tactical, and even story-driven, than rolling a d6 and saying "my dice was higher than yours therefore I win".
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A skilled DM will also do this when its story-appropriate. I would _NEVER_ have an Orc-King's court pull these shenanigans (outside of maybe one Half-Orc Cleric who the players would be familiar with). But the opposite problem may happen, the Orc-King, upon losing an argument to skill alone, may claim the adventurers were cheating at the argument/debate through magic and it'd be up to the players to prove (to a non-magical being) that they were in fact, not using magic.
Etc. etc.
With skill, you can setup good stories more easily through these interactions.