Researching trolls couldn't lead anywhere but to John Bauer... I am so in love with his stuff. He illustrated the fairy/folk tales I read as a child and they've painted such a strong image in my head. So Grár and his trolls were all covered.
Ísafold is old, so instead of looking at the 1800s for clothing references - like I did for the ghosts - I went back to the vikings. Here's a reference sheet:
The following images all date back to... Ages ago! I was struggling with the visual style and in the end just decided to not try to force a specific style but to just draw what comes out.
These images of Grár show this quite clearly:
Some progress for my troll portraits (which I've posted recently, but still!)
I wanted Ísafold to look kind of regal, very strong, severe and with lots of authority. While I keep referring to her as a "Galadriel-style character" I didn't want her to look anything near a super-slender, long-haired image of perfect beauty. Here's a progress shot: