It's rare...I just cannot find a Barnshe for this quest on the first island for the life of me.
On one hand I don't wanna look at a guide as that ruins the fun, but I'm looking all over Thessalian(probably wrong spelling) Hills and nothing.
While I'm at it, a better quest tracker would be nice. It seems to be greyed out for the time being.
I'll spoil it just in case you don't want to know but you can find it
only on the top floor of the windward fort, and it's like a 1 in 20 encounter there. Only place in Deniz as far as I have seen