Explosive Runes

This spell creates a magical trap in the form of traceries and sigils placed upon a piece of writing that create a magical detonation when they are read. It is possible to detect the presence of explosive runes without detonating them: a magic user has a 5% chance per level to notice their presence, and a thief has a 1% chance per level.

When the runes are read, the resulting explosion causes 6d4+6 points of damage (half with a successful saving throw) to any creature within a 10 ft radius. The reader of the runes does not receive a saving throw. The caster and any other magic user with whom the caster has made familiar the secret pattern of the runes can read the protected document or tome without danger, and the caster can erase them at will. Otherwise, only a dispel magic or similar enchantment will remove the runes before they are triggered.

Note that the item upon which the runes are scribed, if it is not resistant to fire, will undoubtedly be destroyed when the runes detonate.