For a magic researcher, preserving the recipe of a newly-developed magic spell or potion is always a problem. Sometimes, you reach for a recipe on paper and find it torn, smudged, or stained with marinara sauce.
Hoarfrost Treants and Deep Freeze Treants live in the Giant Forest of Winterflake Forest.
If you write on the skin of these two monsters, the writing will never fade away.
Captain Augusque is helping Senate collect the tree skins. If you help, I'm sure he'll reward you.