Why is Werewolf immune?

[Kriegstreiber_KT]

Because monsters is the weakest faction and it's fun watching people that dont know he's immune shoot their own units.

It is the counter unit for the Nilgaard Vipers

 

[Draconifors]

It is the counter unit for the Nilgaard Vipers

And Spell ST, to some extent.
Had three Werewolves on the board, and the ST player literally couldn't damage my units (they used up all weather in R1 and R2).