Hedron Stones of Sending

These Hedrons come in a set of ten. While you
touch one stone, you can use an action to cast the
sending spell from it. The targets are the bearers
of the other stones. If no creature bears another
stone, you know that fact as soon as you use the
stone and don't cast the spell. Once sending is
cast through a Hedron stone, the recipient of the
Sending cannot reply without using their Hedron
stone. Once used, it can't be used again until the
next dawn. If one of the stones in the set is
destroy