I another post someone mentioned that monsters in the Witcher RPG (IIRC) have two entries for lore:Researching the enemy's weakness is a good idea. But,of course, the SMART monsters are going to use deception and there might be some mistakes in the local folklore....
Maybe the local vampire is only affected by SILVER holy symbols, but pretends to be affected by all holy symbols. Maybe he can cross "running water".... but he just chooses to stay on his side of the river (It's a courtesy to another monster who lives on the other side).
I once did something similar with a vampire that could Polymorph. She would disguise herself as a Bard and spread songs/rumours about a rare vampiric weakness: unable to cross a threshold, or exit the coffin if a rose was placed upon it. The PCs broke into her lair and were surprised when the vampire actually loved roses .
- Folklore: what common people know about monsters and a good bit of it is wrong
- Hunter Lore (i.e. what the witchers know): more accurate information about strength's and weakness