This is so weird. You've created a problem for yourself, for no apparent reason, and now you need the DM to help you out of it?Hang on a tick. I asked you a direct question.
What action can I, as the paladin player in the game, declare in order to succeed? You keep insisting that the players MUST declare actions. I honestly don't know what actions I can declare here. I really, really don't. So, I'm asking you directly, as the prime advocate for this style of play, what action can I declare in this situation?
I don't need brush offs or sidebars about unrelated stuff like how it doesn't bother one DM that I use OOC knowledge in game.
I am DIRECTLY asking, "What action can I take to allow my paladin to learn/know that Intellect Devourers can be hedged out by Protection from Evil/Good"?
If I say, "I ask the wizard if Protection from Evil/Good will hedge out these creatures", that's good enough for an autosuccess in your game? How did you know that the wizard knew that?
If you want to learn that information, maybe go to a library or a sage if the party wizard doesn't know the answer?