Divination Crystals

Divination crystals are large crystal structures where a person can stand at or on, and talk to another person. Charged by lightning magic, the crystals will also show the person's image at either end. A true name is needed to activate them, including the person they look to communicate with.
ACCESS/AVAILABILITY:  How or when the crystals were first discovered was not recorded, at least in anywhere anyone knows off. It has been in use by some of the oldest civilisations for centuries and only in the Material Plane. Found throughout rocky underground regions in old ruins or old cities.
COMPLEXITY:  It is heavily controlled and only a few are known. Nearly every one has a heavy presence of sapient species defending it, including in the old ruins. Most are used by Dwarves & Black Elves with the odd other one controlled by far darker & dangerous creatures. One or two are controlled by dragons or their minions.
UTILITY:  The crystals are both easy to use, and nearly impossible. As long as regular lightning based magic is used on them, the crystals will theoretically work. Depending on the exact set up, they need to be touched if no crystal base is present. If there is, it is stood on. The harder part is that the name of the person at the other end must be the true name. The person picks up that they must access one and activates the closest at their end. When this is done a magical connection is made between the two allowing both parties to see and hear each other.

"Can be hard to use those crystals. If you don't have the true name, or it's not charged, then it's impossible to use. Also, many of them are found in out of the way places and guarded by less than friendly groups."
Floki Bigbeard, talking to the Hofgothi of Uppsala, shortly before his death.