By tracing these mystic runes upon a book, map, scroll, or similar object bearing written information, the wizard prevents unauthorized persons from reading his material.
The explosive runes are difficult to detect - 5% chance per level of magic use experience of the reader; thieves have only a 5% chance. But trap detection by spell or magical device always finds these runes.
When read, the explosive runes detonate, delivering 6d4 + 6 points of damage to the reader, who gets no saving throw. A like amount, or half that if saving throws are made, is suffered by each creature within the blast radius. The wizard who cast the spell, as well as any he instructs, can read the protected writing without triggering the runes. Likewise, the wizard can remove the runes whenever desired. Others can remove them only with a successful dispel magic or erase spell. Explosive runes otherwise last until the spell is triggered.
The item upon which the runes are placed is destroyed when the explosion takes place, unless it is not normally subject to destruction by magical fire (see the Item Saving Throws in the Dungeon Master's Guide).