I’m in a game where the DM decided that Monster Perception DC should be based on table 10-4 instead of the rules starting on the bottom of 291. Apparently there is enough ambiguity in the language for either interpretation. I would be grateful if this could be clarified. Thanks in advance.
Their perception DC is 10 plus their perception score. Just like everything else that has a DC now.
Where is the ambiguity?
As GM, it’s up to you to set the difficulty classes (DCs) for rolls that don’t use a predefined DC.
How does the table, combined with section 3 on page 291 not defining the DC for perception. There is even an example.
For tasks opposed by another character, the DC is based on one of the target’s modifiers, as defined in the task. A DC derived in this way is equal to 10 plus the creature’s modifier for that type of roll. All modifiers, bonuses, and penalties that would apply to the character’s rolls for a task also apply to its DC unless noted otherwise. For example, if you’re trying to sneak past a guard, you attempt a Stealth check opposed by the guard’s Perception DC. If you have a +5 Stealth and they have a +3 Perception, you roll 1d20+5 against their Perception DC of 13.