The Shards of Tavish (TA-vish)

So long as rune-engraved shard of this glass is used in the construction of a reflective surface, the enchantment imbued onto the glass will create a means of communication reflecting the user, their voice, and their immediate surroundings between one user and another. Once a connection is established between two runes, both users can allow the enchantments to "resonate" with each other revealing the location to the other user.
Although this item requires a user to attune to it, the person utilizing the shard-imbued item does not need to know the other person on the other end of the shard to make contact, but the receiver may choose to decline or even break off the communication line to the particular shard and its user preventing the person from contacting them even if they were to utilize another shard. The only way around this is to utilize an item that is combined with bloodcoral magic, this is the only way to override a block.

Rarity

Originally, there was a flourishing and valuable trade route that was established between the Ember Strand and the rest of the continent. With the ease of communication, the people of the Southern Sands were able to access many resources that are scarce in the desert but valuable from elsewhere. Trips for merchants traveling there was almost assuredly a profiting one and eventually luxury items- even if most were secondhand- were beginning to make it to nomadic groups that never had access to such wares before.
However, after a devastating war between two desert city powers that resulted in the crippling damage to the Ember Strand, it was said that the members of the Tavish family perished in an effort to evacuate many members of the region and neighboring areas as they could revealing the true extent of their strength and power. Their family seat and stronghold were set ablaze when the warring sides reached the region and the desert palace was plundered for any artifacts that were left behind.
Years after the war ended and trade was eventually re-established, many found communications to be a mess and difficult to organize. In addition, there were no new glass shards distributed across the continent. Realizing what could have happened, those in position of the remaining shards and imbued items stored what they had in family vaults with searches beginning to find a pair to create a communication line specific to the family.
Almost a millenia after the end of the Tavish line, the shards are revered as incredibly rare relics.

Utility

While other families have made and created glasses that have been distributed, they were incompatible with most other magics and lost their enchantments if combined with another. Arcanists believe that there was a secret ritual or power source used by the Tavish family that allowed the Shards of Tavish to endure other magical effects.
Because of the versatility of these shards items, many have created private lines of communication.

Social Impact

For nobles, owning at least two shards of the mirror and having a designated diviner wield it as well as shield against any invading divination magic is seen as a luxury. Because of its ability to communicate with any surface that has the rune, only those highly trained in arcana
Guilds, institutions, adventurers, and other explorers have all raced to buy any shards that have appeared (or are rumored to have appeared) in local high magic supply shops or in underground markets if one has a connection. However, due to the short-lived and dangerous occuptions that many embark on, these normally end up either lost or shattered.

Inventor(s)

No one knows who created the rune and while many Southern Sands noble families claim to be descended from the house that had discovered it, only the lost Tavish bloodline that resided in the Ember Strand had mastered the ability to apply the runes to not only mirrors but into any reflective surface albeit temporarily in the case of the latter.
While many others mages in the Southern Sands are able to replicate the technique, these runes did not last indefinitely as the Tavish runes did and so, in the early years of the High Mageocracy, the rune was renamed from the "Longspeak Rune" to the "Rune of Tavish".

Discovery

According to records and family stories of local nobility, the powerful rune that empowered the Tavish mirrors was discovered etched into flat stone walls of deserted caves on the western border of the Southern Sands before the Early Mageocracy (a time when mages were beginning to harness the magical energy of Auriga).
Nowadays, many scholars that study this area of divination magic spurn the idea that this powerful rune emerged from the nomadic mages of the region, believing that such a high level of magic could not be attained when resources for the arcane were so far scattered in that land. Instead, they attribute this magic to the long lost Aestrella people- a lineage of elvenkind that had ties to the aether and connective magic