Don't know what to do...

I am just about to fight Grandmother Silk. I feel like I explored all of the previous areas, well everything explorable with my current ability set. I'm still missing the map however for the area above Bilewater. I have done all special courier quests too. Is there anything else I can do?

I have also been told there is a quest I can do which makes the Grandmother Silk fight way easier. But I can't figure out what it is or how to activate it.

So, right now, I'm kind of stuck. I have explored all areas for secrets, but it seems you need a different ability to gain access.

What should I do? Or should I fight Grandmother Silk straight away? Do you have any build recommendations?