Signal Stone

Signal stones are small clay or thin stone tablet, fragile enough to be broken by hand. Each is covered with runes that bind and pair it to another stone of identical design. When a signal stone is broken, its bonded stone breaks in a similar manner. After being used in this way, each stone becomes non-magical.
Signal stones come in a variety of designs, and are made to be broken in different ways to communicate simple messages. A common design might have runes symbolizing "Danger", "Safety" or "Gather" - when broken at the proper spot, it becomes clear which message was sent. Other designs have no helpful runes, and are simply numbered.

As a bonus action, you may snap a signal stone in your hand, or throw it to a hard surface to shatter it entirely. The signal stone paired with it immediately breaks in the same manner. If the paired stone is not on the same plane of existence, there is a 50% chance that the magic dissipates without breaking the other.

Mechanics & Inner Workings

The most common design for a signal stone is a small triangular tablet two inches across. At the tip of each point is a simple rune, with a notch just below so the tip can be cleanly snapped off. These stones tend to have runes symbolizing the following: "Gather", "Safety", and "Help". Additionally, the center is notched such that it can be crushed into many pieces, which usually signifies "Danger", or "Defeat".
This design is widespread, portable, and easily understood by anyone. It is intended for situations where false messages or identity are unlikely. More complex designs include a wheel-like design with many numbered spokes, so many different messages can be sent. One or more of these can be used as a sort of simple key phrase or password system before other messages are sent. Encryption and secret rules are often used to confirm identity, but such designs can become expensive over time.

History

Signal stones are widely used by military organizations, guilds, and some adventurers - the ability to send a simple message across vast distances without the need for mage is an indispensable asset to whoever can afford a regular supply of signal stones.
However, this convenience comes with some downsides compared to sending spells - stones can be stolen, false messages sent, accidentally broken, or simply lost. This lead to the development of simple methods of encryption - later signal stones began to be designed with their meanings obfuscated so that false messages were more difficult to send.

Item type

Consumable, Magical

Rarity

Common

Weight

1 oz

Dimensions

2 inches by 2 inches