Sending stones were magical items that allowed remote communication over any distance, even across different planes. The stones always came in pairs, and were smooth and delicately carved to match each other. If one stone from the pair were destroyed, the other would lose its magic.
When activated, a sending stone could be used to cast a sending Spell targeted at the bearer of its pair, relaying a short message telepthically. If the receiving stone had no bearer at the moment of the casting, the stone did not cast the spell and made the user aware of it. This power could be used once, after which the stone regained its magic at dawn.