A resonance crystal is a crystalline structure that gives mana mass, allowing one to work with it. The needles used by bioarcanic engineers contain a resonance crystal embedded in the metal, and many powerful artifacts have been found with these crystals integrated into their design. It’s believed that the Crystalpoint Lattice is made of resonance crystals, but out of respect for their leadership no one has asked to study them.
No resonance crystals have been manufactured in this cycle — all known crystals have been excavated from ruins of previous cycles. Many researchers posit that the crystals form naturally in the interstitial place between realms, but no one has been able to confirm or deny.