Sending Stones

While you touch one stone, you can use an action
to cast the sending spell from it. The target is the
bearer of the other stone. If no creature bears the
other stone, you know that fact as soon as you use
the stone and don't cast the spell.
Once sending is cast through the stones, they
can't be used again until the next dawn.
If one of the stones in a pair is destroyed, the
other one becomes nonmagical.