This is a form of protective rune that is placed on books, doors, etc. The rune activates whenever the activity associated with the object is done. When a door is opened, a portal walked through, a page read, a chest opened. The action usually depends upon where the rune is placed.
Area may be manipulated by doubling as normal.
The rune is inscribed by tracing with the caster's finger. If the rune is inscribed in the air, then it affects the first creature to walk within 5' of it.
Damage done is 1d8 per spell level. The rune's duration is until activated. The explosion only affects one creature. The rune can only be seen with magical sight.