how do i get one? i tried casting it but it says you need to be a protagonist. Whats that? also can you tell me where to get the rest of the bow that you make from the shaft in the tanner shop in the bridge district of athkalta?

Only your lead character can have a familiar, so you can only have one if your lead character is a sorcerer or wizard and they can cast the spell (either from a scroll or from memory).

About the bow...

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You'll have the chance to find it when you go to a deserted island later in the game (Chapter 4). It's in a looney bin. :D

Ah, thanks.