You can receive these once you've begun the Test of Octec's Ghost at a University of Architecture. You will be given two crystals and can pick up two more at the School of Architecture.
Once per 24 hours, you may request crystals from a School of Architecture, up to 4 more times, for a total of 12 crystals. All the crystals you receive will be of the same type. You will need to trade with other players to complete your set of 20.
There are 20 types of crystal hieroglyphs.
- Amen Ra
See Test of Octec's Ghost for trading information.