There is a hag in my game who is posing as a quest-giver, sending the party out on missions that sound reasonable at first but end up spreading misery when they do them. I have a moment planned in the plot when another NPC reveals the hag's identity, but the players are at least starting to think that the hag isn't
good. So I started wondering about how I should reveal it if they start asking the right questions.
Bestiary Ability Glossary wrote:
The monster's transformation automatically defeats Perception DCs to determine whether the creature is a member of the ancestry or creature type into which it transformed, and it gains a +4 status bonus to its Deception DC to prevent others from seeing through its disguise.
I don't understand the difference between the Perception DCs that it auto-defeats, and what it gains a +4 status to. My best understanding is that I don't have to roll secret checks in the background every time the players meet her, but if they express doubts in a specific way that leads to the check, they can roll the check and the +4 status bonus is applied. Is that right?