Blank Crystal

One of the most revolutionary findings of Edens's history is the Illuminous Quart, or blank crystal if you're not a gemologist. Discovered during the end of the Kingdoms and empires age dwarven miners within the highlands found and sold one of these crystals, thinking it wasn't special but could fetch some gold, and an elven mage named Tolmir Advomandel noticed its capabilities to hold and emit magic fed into it better than most artificial constructions. He purchased more of these crystals, as they were easy to find, and gathered other mages to experiment on their capabilities, which drew the attention of other mages as they showed their findings off to others, and in a few years, mages were able to come up with creative ways to use the crystal.
 After making a buzz within the kingdom, the dwarven kingdom started to find more of the crystals and even used them for their own means. Other parts of Eden also picked up on this, and miners (desperate to potentially capitalize on this discovery) tried to find the crystal, and to many surprises, it is easily found in caves and they come in large quantities. Soon enough, the kingdoms and empires of Eden sought to regulate the distribution and utilize it for themselves, and it eventually became a common item within the world.
These crystals can be used for a variety of things:

• can project themselves when connected to another crystal
• can emit magical effects (magical barriers, lingering traps, be used for light, etc.)
• could be used for teleportation or negate teleportation
• could inhibit magic if done right

This crystal completely changed the lives of not only communication and transportation but the quality of life of the people (that could afford it).