Dimensionfold Wiki

Any fist-sized cube of pure graphite.

Because graphite is highly anisotropic to electromagnetic and sonic waves, it yields a polarization effect in the space-time of any localized extradimensional space such as a portable hole or bag of holding.

This polarization allows two such extradimensional spaces to be positioned in a nested, overlapping, or touching position without invoking the typical mutually assured destruction.

The positioning is a delicate matter requiring a successful DC 15 Dex check