Fria Ligans forum

I've read several official Vaesen adventures and, so far, haven't noticed the narrative exploring how the investigators defeat their Vaesen foes. Does this mean that as soon as the nature of the Vaesen is known, the PCs automatically know the ritual required to defeat it?

The PCs may through some research find old stories about what to do, but some basic lore is known by the society. To reflect that, the information in the vaesen art books (by Johan Egerkrans) is known by the society (page 7 in the rulebook).

At our table, we play more in terms of character banishing väsen more than "defeating" them. And as to knowing all väsen, that would be like asking a physicist of all matter in the universe is known; our investigators of the society know some of what is known about some of the väsen, but knowing all of them? That seems an impossibility in the spirit realm just as much as knowing everything about something in the material realm. Knowing everything means there is nothing left to learn, nothing left to know, nothing left to discovery... and no mystery left to investigate.