So my players have been hired by a wizard to recover 3 copies of a spell he created.
Three other wizards have copied the spell into secondary spellbooks (which required them to break a copy-protection spell he placed on the scrolls he sold them). They're then making scrolls/magic items of the spell and undercutting the wizard's prices.
Of the three, two were students at the Mage's University. Getting their copies wasn't too hard – one was fairly gullible and allowed the rogue access to his room. She cast sleep using her feminine charms and exited with the spellbook he had concealed. It had his Arcane Mark on it, but was otherwise not really defended.
The next student who had a copy had it defended better: his door had a better-than-average lock, his book was better concealed, and the party had to deal with a Sepia Snake Sigil to retrieve it.
The students were fairly easy. They lived in relatively open dormitories, were kept busy casting for much of the day in their classes (which limited the available spell slots for defenses), and weren't experienced enough to know that a skilled couple of people could essentially walk past the school's existing minor defenses.
The last copy will give them some trouble, though. It's in the hands of the owner/operator of a magic shop. He's got access to a decent number of minor and lesser magical items (no weapons or armor with more than a +2 bonus, but he'll have a decent number of protective items). He's 7th level and doesn't have much in the way of required daily casting – he might do a Prestidigitation in the morning to help him clean the shop and entertain customers, but otherwise will have most of his spell slots.
He's also going to get word very early in the day about what happened, and will likely make the intuitive leap that the party will be after his copy of the spell next.
He does have a few constraints:
- He can't use excessively damaging spell effects, as he's going to be guarding the spellbook in his shop. He is unwilling to risk destroying his inventory.
- He can't kill the party unless they are legitimately trying to murder him. The town's laws do not permit setting fatal traps, even within your own home.
- He doesn't know the identity of the group, or their capabilities. He will know that they can cast Continual Flame, as it was used in the break-in. He may have to use Divinations to find out something about them.
- The town's guard force will not be willing to station guards at his shop, but he does know he can get guards there within 10 minutes if he alerts them.
Within those limits, what steps can a relatively intelligent 7th-level wizard take to defend his secondary spellbook?
Edit:
For those interested, yes, I made a copy-protection spell. A wizard of middling talent but with a conniving mind researched it, and is using it to protect A Spell Called Catherine. I stole some initial ideas (and the Catherine spell) from that article, but plopped it into my world and said, "Okay…what would happen?"
The PCs are in the very early days of the ramifications of this spell, which will be felt throughout the campaign, even after the battle of DRM is lost.
Edit 2:
The wizard landed upon a decent plan, which the characters (by dint of being completely insane) eviscerated. He had 8 decent swordsmen (who cost almost 6x the normal price due to in-campaign reasons) hidden in the 'main' shop (which was full of low-value merchandise, his 'good stuff' being hidden off-site) with Rope Trick while he hid upstairs under Invisibility.
He made copies of the spell, and had his home set up with several fake magical items (with false magic auras). His real items were not easily discoverable.
The party managed to sneak into the shop fairly easily, got up the stairs (spreading caltrops behind them) under the effects of a Silence spell. They proceeded to rob the mage blind, as he *Invisib*ly watched. He made sure they didn't take anything of real value, just the false magic items and the copy of the spell (which he wanted them to have, so he didn't keep getting pestered by groups trying to steal it back).
He was prepared with several spells that would have been able to injure and incapacitate, but not kill, the party. He figured that it would be relatively easy to ensure that at least the one with the spell would escape.
The Silence spell hampered him, as almost every prepared spell he had left had verbal components. He didn't predict Silence, and didn't have anything ready to handle them while that spell was active. The spell didn't end until just before the party left. They declined to go down the stairs again, instead using an Enlarged dwarf with a flaming urgosh to batter a hole in the wall. With a little bit more magic and some lucky rolls, they avoided immediate capture.
The wizard minimized his losses to effectively nothing, suffered no real damage to his home or business, and had several minutes to study the party. The party will not find him so easy a mark the next time.
Best Answer
The best way for the wizard to defend a spellbook is the same as the best way for you to protect your precious computer files - have multiple backups.
But, if he hasn't had time to make a copy, if he knows someone is trying to steal the book back, he wouldn't leave the book in the shop overnight. He'd keep it on himself, likely guarded by as many guards as a 7th level wizard can afford to hire on a temporary basis.
If he must leave the book in the shop for plot points, he'd certainly have the book very well protected and secured. He's 7th level, so he knows 4th level spells. He might, for example, use Stone Shape to fabricate a 'doorless' safe in a wall or floor block. And he'd certainly know to keep the book in a lead box to block scrying and detection attempts. He could also use illusions to hide/conceal the book. And decoy books and safes to waste the thieves' time. And of course, a 1st level Alarm spell on the shop would work wonders. He might hire a dozen men at arms who hang out in a neighboring building waiting for the alarm to go off.
You say he can't use anything too damaging in terms of traps. Well, poison gas doesn't cause much physical damage and dissipates after a while. And while you say its illegal for him to create fatal traps, a) he may not care, b) bribes and Charm Person can get the well-to-do out of trouble, and c) dead thieves can't report you to the town guard. If you don't want to do that, you can always fill the shop with a Web.
Beyond defending his shop, since he knows there's likely going to be a break-in, he might have a familiar watch the shop from a distance and follow the thieves back to their home/inn/hideout. And when they aren't looking, he can rob them blind.