The Tomes of Xorex Xaf

These tomes come as a pair. One book is a deep blue, and the other is a dark crimson. To activate the magic of the book, and copy from one tome to the other, the user of the book must speak the command words aloud.

The command words are "We Bah We Hah Woo Shh Hah Shh".

Whatever is written in one book then appears in the other. This magic works regardless of distance, and regardless of planar travel.