Sending Stones

While you touch 1 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 1
of the stones in a pair is destroyed, the other
1 becomes non-magical.