I haven't done much Leathercraft, but I found a recipe somewhere and thought I'd post it for those of you who have:
Leathercraft 83
Result: Ruszor Leather x1:
recipe #1:
Dark crystal
Willow Log x1
Ruszor Hide x1
Distilled Water x1
recipe #2:
Dark crystal
Windurstian Tea Leaves x1
Ruszor Hide x1
Distilled Water x1
Result: Ruszor Leather x3:
recipe #3
Dark crystal
Tanning Vat
Windurstian Tea Leaves x 3
Ruszor Hide x 3
Distilled Water
Like I said, I can't make these as I have very low Leathercraft skill, so if there's an error in my post, please just post a correction.
This leather is apparently used in some of the Fey weapons.