What does the Elgriffin special training challenge mean by equipping all +40 defense gear?

They mean enhancing all of your gear to +40 with black stones and/or black crystals.

Where i can obtain the pristine black crystal armor?
Rp thank..

How do you get pristine black crystal armour

go to your camp
(pic left to right below)

then go to Refinery

then pick craft black crystal (pic 1)

then pick Pristine black cristal armor (pic 2)

then fuse your all armor cristal until reach 100% to make 1 pristine black crystal armor (pic 3)

Thank you