Touchstones

For more than a thousand years, since before the time of Dolure the Abstruse, natural philosophers have sought the Common Tongue -- that mythical linguistic wonder that would bind together all peoples. It must exist, reasoned many, simply because it would make things so much easier. Alas, many a treatise later, the world has still not seen this elusive efficiency, despite several attempts to create one with alleged divine inspiration.
In the meantime, people from different lands who wished to communicate with each other simply languished without communication... no, wait. That's not right. Practical people devised all manner of solutions from the basic (if time-intensive) expedience of simply learning other languages to magical workarounds. Of the latter, none has been more useful, nor lead to bloodier wars than the touchstone.

Utility

All participants in a conversation must remain in contact with the stone during a conversation. This is usually accomplished by sitting across from one another and touching one's fingertips to the stone. Vessuna will sometimes use their tails instead, as they tend to talk with their hands.

Manufacturing

Arcane apprentices get sick of churning out touchstones, but it is a large part of their "training." It does, it must be said, ingrain some ritual habits that later allow their attention to be focused on more important things in the course of working more complex spells.
Polished stones are preferred, but not required. Any old rock will do. As a related aside, some communities far from urban centers will have a large "meeting stone" at the boundary of the village rather than individual touchstones. There they invite outsiders to come and talk to an elder or leader, often with both hands pressed flat against the stone between them as a show of peaceful intent.

Access & Availability

Touchstones can be had on the cheap on every street corner in every civilized place. In an odd twist, it's rather harder to make a convincing knock-off than it is to just create a touchstone, so there's little market for fakes. (However, there are those who create false touchstones as a practical joke item. Rather than delivering actual translations, these stones are programmed with a store of set phrases on a theme such as insults, parental nagging, or nonsensical platitudes.)

Complexity

The dumbest troll can use a touchstone. But just try convincing one to.

Discovery

The wizard Noeline stumbled upon the idea one afternoon over their tea. "If," they pondered, "we can use a rather simple spell to comprehend unfamiliar languages, then why would we not just create a magic item that would let people do this all the time?" Like most breakthroughs, it looked stupidly obvious in retrospect. Why hadn't arcanists been doing this since the inception of magic that crossed language barriers? We will, of course, never know.