shadowdancer lore

I was planning to do a shadowdancer in my next run of baldur's gate.

But I could not find too much information about it on the net.

I wanted to know if the shadowdancer had to learn his ability or it is innate like the sorcerer?

Is it tied to mask or shar? Or can you become one on your own?

This is roleplayer question, just to flesh out my character.

So if @LadyRhian or anyone else who know about shadowdancer can help me that will be great.