Greenfield
Adventurer
As written, you can put as many on that sheet of paper as you like. No limit.SRD said:Explosive Runes
Abjuration [Force]
Level: Sor/Wiz 3
Components: V, S
Casting Time: 1 standard action
Range: Touch
Target: One touched object weighing no more than 10 lb.
Duration: Permanent until discharged (D)
Saving Throw: See text
Spell Resistance: Yes
You trace these mystic runes upon a book, map, scroll, or similar object bearing written information. The runes detonate when read, dealing 6d6 points of force damage. Anyone next to the runes (close enough to read them) takes the full damage with no saving throw; any other creature within 10 feet of the runes is entitled to a Reflex save for half damage. The object on which the runes were written also takes full damage (no saving throw).
You and any characters you specifically instruct can read the protected writing without triggering the runes. Likewise, you can remove the runes whenever desired. Another creature can remove them with a successful dispel magic or erase spell, but attempting to dispel or erase the runes and failing to do so triggers the explosion.
Note: Magic traps such as explosive runes are hard to detect and disable. A rogue (only) can use the Search skill to find the runes and Disable Device to thwart them. The DC in each case is 25 + spell level, or 28 for explosive runes.
But if you look at Dispel Magic, you may want to pay the man the few coppers and buy the extra paper. The targeted version of Dispel always succeeds at dispelling your own spells, and the area version will only affect the first enchantment it finds on an object or creature, starting at the highest level spell. That means that only the first set of Runes will go off, destroying the rest in the explosion.
So oddly, the Boccob's Blessed Bomb trick will be a firecracker, not a mortar shell, if it works at all. By the RAW, the area Dispel doesn't affect magic items.
Better to wad a bunch of trapped pages together around a stone (to weight it for throwing), then throw it. When you light that baby up with your area Dispel, you get to trigger all the Runes at once, since each is a separate page.