Date is today. Did you just write this thing on the spot

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I know what you mean with immunities. Let me explain what exactly I want to do maybe.
Encounter a dryad, she wants to save her forest from something. If you accept, is ok. If not, she tries charm person on you. There I wanted to try the save. However, there are so many variables to think of. Perhaps PC has found an immune to charm cloak, or anything like that. What happens then... a mystery before test

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An easy way, would be to just check for the wisdom of the player, or a charisma depending on the charisma of the dryad. Tweak with the rules or something, to get a result.
The only issue with this, is that my campaign is a little open world. So you could encounter this at level 5 with 16 charisma, or at 15 with 20. But I guess it shouldn't be an issue that much, for if you do the quest so late, you'll also get the same xp. So, auto success save, little xp

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In any case, I will try the script, thank you for it. Will let you know how it went when I do.