I am trying to figure out how the spell planar inquiry actually works, specifically, if it is using some divine-like power to learn things, or just to relate things it is physically capable of finding out. For example:
" When you call a creature using planar inquiry, the only task that you can ask of the creature is for it to answer questions or gather information regarding a specific topic (a person, a place, or a thing). After hearing your request, if the creature has an appropriate Knowledge skill, it can attempt a check to provide the information it has. "
If my party is asking a question about the BBEG, and the outsider has the right knowledge (lets say knowledge local for a humanoid) does the outsider just already know things about the BBEG, even if they had never heard about them before? Or are they using this skill to do something like seeing into all of creation?
Also, if they fail, do they just say "sorry" and leave, or do they then go on to step two?
" If it lacks such a skill, the called creature leaves for 1d4 hours to gather this information. Upon its return, you roll 1d20 + your caster level, and use the result to determine what information the creature has gathered about the subject (as if using Diplomacy). The called creature stays for up to 10 minutes as it relays this information to you, after which it departs to its home plane. If the creature is attacked or damaged at any time during the spell’s duration, the spell ends and the creature returns to the plane from which you summoned it. "
If the party asked "where is the BBEG" and the outsider does not have that skill (or fails?), does the outsider physically go to where the BBEG is? Can the outsider do this unerringly, or does it require them to have some ability to find them? Do they do so in the material plane, the ethereal plane, or by looking through their deity's omniscience? Are they spells that could protect someone from this kind of observation, or is this spell meant to be the absolute trump card and way to learn anything you want?