Can't kill wyverns anymore?

[jan]

I used to be able to kill wyverns with my rod of icestorm, but suddenly can't - at least in Navar, one of the warehouses on the harbour. What's happened?

[bort]

Perhaps because of a no magic area?

[jan]

No, magic works. But apparently the first wyverns you meet in there are more resistent to cold. In the end I found out that I can kill them with bombs.