The Royal Envoy feature for Purple Dragon Knight seems to be a bug. Currently, I am allowed to choose between the proficiency of Animal Handling, Insight, Intimidation and Performance while I do not have proficency in the Persuasion skill. The Royal Envoy feature states:
At 7th level, you gain proficiency in the Persuasion skill. If you are already proficient in it, you gain proficiency in one of the following skills of your choice: Animal Handling, Insight, Intimidation, or Performance.
I was playing around with character builder and made a warlock with the eldritch invocation beguiling influence (grants proficiency with deception and persuasion). I was able to choose the proficiency (Animal Handling) for the Royal Envoy feature. But after I removed the beguiling influence invocation, I still had the Animal Handling proficiency. Even after removing the fighter class and choosing the class again, I am still able to choose a proficiency.
The skills granted from my character's background are Athletics and Insight. The skill granted by my race feature is Medicine. So, I do not have any other feature that grants Persuasion.
The Royal Envoy feature for Purple Dragon Knight seems to be a bug. Currently, I am allowed to choose between the proficiency of Animal Handling, Insight, Intimidation and Performance while I do not have proficency in the Persuasion skill. The Royal Envoy feature states:
At 7th level, you gain proficiency in the Persuasion skill. If you are already proficient in it, you gain proficiency in one of the following skills of your choice: Animal Handling, Insight, Intimidation, or Performance.
I was playing around with character builder and made a warlock with the eldritch invocation beguiling influence (grants proficiency with deception and persuasion). I was able to choose the proficiency (Animal Handling) for the Royal Envoy feature. But after I removed the beguiling influence invocation, I still had the Animal Handling proficiency. Even after removing the fighter class and choosing the class again, I am still able to choose a proficiency.
The skills granted from my character's background are Athletics and Insight. The skill granted by my race feature is Medicine. So, I do not have any other feature that grants Persuasion.
I tested on a Fighter character with no Persuasion proficiency from any source. I see the "Choose a Royal Envoy Skill" selection even so.
It might be due to the Persuasion skill also being granted double proficiency, which complicates matters.
Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)