Yeah, I knew of the display case mod before I did this.
Would it be possible to place the useless artifact, say, outside your fort surrounded by cage traps, and then wait for a kobold etc to steal it and then get caught in the traps? I forget, do kobolds lose their trapavoid after they have stolen something, or do they have to be spotted first? If they have to be spotted, this could be prohibitively difficult. This would also rely on the thieves going for the artifact, which I think shouldn't be a problem as they like to steal valuable things, right?
There is also a certain justice in using the artifact's creator as it's pedestal...
Hm. Kobold idea does have legitimate potential although it would probably
require a lot of patience, effort and luck be pretty dwarfy. Kobolds don't lose their trap avoid even after they are spotted, so you'd still need a cave-in to knock it into a cage once you know it's picked up the artifact. Knowing when the kobold has picked up the artifact is the tricky part, because the game will only announce the theft after the kobold leaves the map (if the kobold isn't spotted first). If the kobold is spotted before the theft it'll simply abort the attempt.
So what you'd need is to seal off your fortress so that the only stealable item is the desired artifact. I'd probably put it at the end of a long corridor with cage traps and cave-in system running down the entire length, pretty much like what I already did in the movie although longer and narrower. Kobolds seem to come in a defined kobold-season around the arrival of caravans so you'd know when to be on your guard. It'd still be fairly crazy to stare at the artifact mug on the ground waiting for it to blink out of existence when it goes into a kobold pocket. The most sensible thing to do would be to take regular saves and once it gets stolen revert to the back up before and then concentrate on the artifact because you'd know fairly closely when it would be taken (in case it wasn't already obvious, I save-scum like crazy). And then you just need to save scum your cave in attempts because 9 times out of ten they kill the subject or throw them in the wrong direction or not at all.
Of course, there is another major disadvantage to the kobold system. The whole aim is to make an artifact display case. Not an artifact-and-dwarf or artifact-and-kobold display case. The ambience would be spoilt if there was a dwarf begging to be let of the cage while you're trying to admire the legenedary work of art in his fist. And if it were a kobold it might swallow the artifact out of spite so that your dwarves wouldn't be able to see it (sounds like one of the old Power Goals). The appeal of doing it with dwarf power (other than the practicality and relative ease) is that a dwarf will fairly quickly die of thirst if you so choose, and you can then remove the body and leave the artifact inside*. A kobold will not starve so your only other option would be waiting for it to die of old age. A kobold has [MAXAGE:150:170] so if you were going to try that I'd be very impressed. I may actually try it. The capture kobold holding artifact bit, not the waiting for death by old age part.
Another option is possible if you have thieving animals on your map. If you have for example Kea on your map then
you have my condolences you can set up something simpler that doesn't require a cave-in. You have a cage-trap-less entrance corridor that passes the artifact and then has a cage trap before the exit. When the creature enters you lock the door behind them (or raise the bride, whatever) so they are forced to walk passed the artifact and then over the cage trap on their way out. Of course, you again have the problem of waiting for the creature to die of old age but thieving animals mostly lead shorter natural lives than kobolds, I think. If you have thieving animals at all. I only seem to have giant insects and giant birds on my embark so I probably won't bother doing a movie of an animal artifact steal. Although, if a Kea stole one of my artifacts and I caught it in a cage, I think it would be funnier to tame the Kea so that it would forever strut about the fortress with the mug in it's beak. Mobile-artifact-display-animal. Oh shit. That's awesome. Maybe I will try that. With an artifact weapon so that the Kea is carrying around an artifact steel sword like some sort of militia straight from The Far Side.
Here's one concept.
Make a ring of traps like so.
^^^^
^++^
^^^^
On one of the floor tiles, put a stockpile that accepts only Artifact quality Finished Goods.
On the next tile, pasture a Giant Cave Spider. The pasturing will keep it from wandering onto the cage traps.
Enjoy your kobold zoo!
That has potential too although I think many people underestimate the difficulty involved with making GCSs do as they wish, either tame or otherwise. I haven't experimented much with them myself. The problem I see with your example is that the GCS won't shoot webs at a kobold it can't see, and a kobold it can see won't try to steal the artifact. If you're relying on the kobold stealing the artifact and then being spotted and webbed by the spider while the kobold is standing on a cage trap, well...Your crazy mouse-trap plans are more complex and ambitious than mine dare be. I prefer indiscriminate cave-ins for creatues that can be knocked out.
Also, using artifacts as thief bait inside trap rings is a waste of time: goblin thieves only go for the kids, and kobold thieves are [TRAP_AVOID]. Using them as thief bait behind a one- or two-tile wide hall with chained dogs and military stationed nearby works though.
You may have missed the aim. It's not for ways to catch thieves in cages by using artifacts. It's for proven and reliably repeatable ways of getting an artifact into a cage, and only the artifact in the cage. Bonus if a dwarf doesn't have to die, but so far the only way I can see to avoid a dwarf death is waiting for an animal to die of old age or a kobold. Many forts don't even last that long so it's less practical than even the method required to get a kobold or a wild animal into the cage with an artifact to begin with.
* THIS IS STILL THEORY Once my dwarf dies in the cage I will either confirm or dismiss it. If it's wrong then the display case is a failure in my opinion.