Everyone, every thing has a weakness. But not all of them are obvious. This can be in the dungeon, on a job, in war...

It's why bishops are valuable. I'm not certain if all of them have it, but they can take in information quickly; scanning so to speak.

Rooks can not, Queens can not, neither can Kings. I don't know much of what Knights can do though.

[Not that she doesn't have people who are knights, but she rarely gets to talk about it. They're mostly physical but they might have interesting quirks.]