Farspeaker

This spell enchants two or more specially constructed boxes so that words spoken into one will be heard from all the others. The boxes must remain within one-half mile per level of the caster, to a maximum of 5 miles. Boxes taken out of range will become functional when brought back into range

The boxes must be constructed of a sturdy ceramic material and filled with a fine silver wire; the cost is about 100 gp each. They are roughly 8 inches square and weigh about two pounds each. The boxes are reusable. The wizard must touch each box in the course of casting the spell.

The material component is heart's blood from a hydra with at least as many heads as the number of boxes to be activated.

Notes: Common for artificers; otherwise very rare. (Updated from Polyhedron Newszine.)