How can I finf the glittering stone?

If you are referring to the "glittering stone" that you need to find in Guild mission 13 (found in the chapter 4 list) call "Collector's Plea, You have to find a Griffin in that level and defeat it. After doing that, a chest will appear right next to you and inside will be the said "glittering stone". Simply take it back to the start of the level and place it into the collection box.
If this is your first time attacking a Griffin, I suggest loading up on the following: potions, hi-poitons, and hawkeye gems. (I forgot if you can even get hawkeye gems when you first get this mission, but check anyways.)
The actual fight with the Griffin can be a painstaking task, often taking about 3 to 10 minutes, depending on your style, gear, and skill. It has many attacks for both close quarters and long range combat. All of these attacks can be blocked with the shield, but it is important to note that some attacks, such as the Griffin's long range wing blast, will still do a reduced damage, even if you use the shield.
Attacking the Griffin requires to always be ready to dodge or block, one hit can often chain into an annoying combo that often take you down to very low health.
The most annoying thing of the Griffin is that it is able to destroy your items with one of it's attacks. I usually see this move used as a mid to long range attack. The Griffin will charge in a straight line, and will often turn slightly in order to line up with the player, then kick out both of it' feet. If it connects, not only is the player damaged, but a notice pops up saying that an item was destroyed.

This is why the Hawkeye gem is key for this fight and any fight that includes Griffins. Hawkeye gems take the place of any item that was to be destroyed, so you lose the gem instead of a potion or sacrifice charm.

Every player will have a different approach when facing this creature. I happen to use a one-handed sword and shield combo. I am level 52 and these guys still cause me problems, haha. I use basic attacks more than any battle art, due to the fact that the Griffin can raise high into the air and take off to the other side of the map. (pretty much saying that battle arts can sometimes be pretty slow) Just keep hitting and dodging at the right times, and with a little luck, you can finally kill that flying pain in the butt.

Happy Killing!
-The Arcana Alchemist

Kill griffin to get glittering stone