[RPG] How does one become a god

Incantations

Unearthed Arcana has rules for Incantations, rituals similar to spells that can be performed by anyone. And, since Unearthed Arcana is one of the books released under the Open Game License, all of those rules can be found on the System Resource Document.

The rules are silent on this.

In practice, I've seen it both ways, depending on whether the group takes a more gamist/metagamey approach or a more simulationist approach. "Open rules" games just have the GM tell you "that fails" if it's invalid on its face (only concealing the reason if it plays into the challenge, like "Charm Person fails... I wonder what that guy is if not a humanoid?" But in general you roll for SR, roll the save, you know why it failed. In our current Pathfinder campaign the GM runs it like this, and whenever it's in doubt a flurry of Knowledge checks fills in the gap.

In a more sim game those things are kept more "under the table" because it's not about the rules challenge it's about the in-game-world reasoning challenge. I ran a 5-year 2e campaign that worked like this.

This falls into the lacuna of other things like "do I know if I made a save vs. a spell" that is undefined so that different games can do it differently based on their desired feel.