quest. you will see when you get a quest. you will need it.
One quest called Arwen and Ellinia (Level 15) give you fairy's wing or piece of ice as a reward. What are they for?
http://sea.hidden-street.net/quests/vicquest_103.php
quest. you will see when you get a quest. you will need it.
They are used to make higher-level wands and staffs, specificially, Fairy's Wing for Fairy Wand and Arc Staff, and Piece of Ice for Cromi (but the last only if you do it in Ellina).
Spoiler!
I sold mine early on, not knowing that I would need it later. Now, they are selling for 500-700k for ICE in the FM.
Make a mule and save it. My advice is make a Warrior mule, as they have the most slots to start with. I have two mules to carry the stuff I need for my shop, and the stuff my Cleric finds.