Sending Stones

Sending Stones come in pairs, with each smooth
stone carved to match the other so the pairing is
easily recognized. While you touch one stone, you
can use an action to cast the Sending spell, with
the bearer of the other stone as the target. If no creature bears the other stone, you know so as
soon as you use the stone and don't cast the spell.
Once used to cast Sending, the stones can't be
used again until the next dawn. If one of the pair
is destroyed, the other becomes nonmagical.