I read a story, The Armor Enchanter, in which a player produced equipment for a party who
betrayed him, at which point he activated safeguards in the items to destroy the party.
Is this possible? Can someone who makes magic items retain control over them even when other people wear the items?
The actual effects that took place, those are all quite plausible. The issue is the wizard’s activating the items used by the other characters, and doing it all at once like that.
The wizard in the story speaks a special word, “Lalilulelo” (itself a reference to Metal Gear Solid, for the record), and all of the characters’ magic items activate. That sounds like a command word item, which is basically the default sort of magic item.
First, the rules suggest that you have to be holding the item for it to activate:
A command word can be a real word, but when this is the case, the holder of the item runs the risk of activating the item accidentally by speaking the word in normal conversation.
This isn’t really explicit, but since only the holder has this risk, it would seem that those not holding the item have no chance to activate it. Note, however, that this rule has a whole host of problems, some of which we’re about to run into.
Activating a command word magic item is a standard action
A standard action is something you can (usually) only do once per turn. And it doesn’t say “speaking a command word” takes a standard action, it says the item activation as a whole does. That strongly suggests that you could only activate a single item per action, even if you have several items using the same word. (This is where the “accidental activation” rule runs into serious problems, because if regular speech can trigger an activation, then you should be able to bypass this action requirement since talking is a free action—a huge boost in the power of such items.)
Basically, if the DM is allows something, it is allowed. If the player says they want to put safeguards into the items they create that
can be activated even when not holding the items, and
can all be activated simultaneously,
then the DM can allow that if they want to.
And as the aside above about the contradictions between the action requirements on command-word items and the “accidental activation” rule suggests, these rules are already on the vague side. Plus, ultimately, the books only offer guidelines for creating magic items.
Not all items adhere to these formulas directly. The reasons for this are several. First and foremost, these few formulas aren’t enough to truly gauge the exact differences between items. The price of a magic item may be modified based on its actual worth. The formulas only provide a starting point. The pricing of scrolls assumes that, whenever possible, a wizard or cleric created it. Potions and wands follow the formulas exactly. Staffs follow the formulas closely, and other items require at least some judgment calls.
So everything a player creates has to be negotiated with the DM anyway.
In this case, the DM was clearly playing along with the wizard’s player to allow these safeguards to work the way they did in the story.
And that is the possibility that combat began in this case. The rules are not as clear as we’d like in this kind of situation, but to my mind, the wizard wanted to take a hostile standard action (activate the items), so this was a combat situation. In order to do what he wanted, he should have had to roll initiative—exactly what he didn’t want to do, because he expected that the barbarian would beat him. The wizard may have had an opportunity to act in the surprise round—allowing him to act before the barbarian or anyone else—but that’s a stretch considering how the rules work. See this answer, and perhaps more notably the chat discussion it prompted, for more details on whether or not this is an issue, and how things (maybe) work.
This is, admittedly, an unclear part of the rules and one commonly ignored—though it tends to run into problems with instant-actioning as the wizard was doing here. Again, DM cooperation makes all the difference.
It took me a while, but I finally found something that sort of applies to this.
In the Complete Arcane, p.141, in the section about spellbooks as magic items, there is a part about various means of protecting them, such as:
Spelltrapped: A magic trap has been incorporated into the book (for example, a burning hands spell that strikes anyone handling the book except its owner). The trap can be set to operate when the book is touched, when it is opened, or when a particular page is read. Any spell appropriate for a trap may be used (see Sample Traps, page 70 of the Dungeon Master’s Guide, for suggestions and pricing).
This sets a precedent for enchanting objects with traps keyed to a specific person.
Following the reference to the DMG, we find that some of the sample traps are indeed simply trapped objects as opposed to room-based constructions.
Thus, with the combination of these two references, it is strongly implied that owned objects can be not only trapped, but also keyed to the owner while triggering on others; though it is only stated explicitly for spellbooks and the indicated samples from the DMG.
Additional support for this concept can be found in the Arms & Equipment Guide, Book of Challenges, Stronghold Builders Guidebook, and a few other scattered references.
You will need approval from your DM as the rules and references in question are somewhat vague as applied to your specific question; as well as some research to figure out appropriate prices and requirements and trigger conditions for "smart" triggers: that is, triggers which can distinguish, for example, between mingling amongst a crowd with casual contact, touching or being touched by people normally in social situations, a combat situation with enemies, and the item being stolen or wrested from your grasp. Should your DM approve, you should be able to craft a trap on your items which only trigger when you speak an unlikely word.
Please note: just as it is very hard to build a foolproof stronghold, it is equally hard to build foolproof traps or protections. As was noted by KRyan, even if your DM allows you to trap your various items and possessions, traps and triggers still function by the rules of traps.
Therefore, should your erstwhile enemy actually survive the trap, or possibly disable it, then they still get to use your item. Also, depending on the nature of the trap, they may still be able to use it regardless of the trap(s) on it, or worse, somehow manage to catch you (or another vulnerable target you can't afford to lose) in the range of effect.
Also note: your DM may include the value of the traps in the total market value of the item, and count all of it towards the ~200,000gp maximum market value limit on non-epic magic items. This would reduce how much function you could pack into said item. Epic items have higher limits on the market value of magic items, should your DM allow one of the versions of the epic rules (DMG or ELH).
