In my Cormyr sourcebook, I introduce a concept called Turning Points.
Turning Points take the concept of the “Defining Event” (from the Folk Hero background, PHB 131) and expand it into full on write ups that describe THE major event in a Character’s life that put her on the path of adventure.
One such Turning Point that will be made available in my next sourcebook update is called “Adventurer In Parchment”. It describes how several enemies of, and thieves preying on, a merchant of Amn were trapped one by one in a magical book–one that the merchant gloated over every chance he got, by turning the parchment pages and having one sided conversations with the victims depicted therein, one to a page, where he describes how he lured them to their doom. Time eventually caught up with the merchant, and his death by old age set the trap book free in the wider Realms.
Eventually it was scooped up by a mage in Cormyr, who’s been patiently freeing the prisoners of the tome for the last several years (and thus a Player Character at some point) and turning them back out into the world.
Thinking about the trap tome…
1. Perhaps it’s truly a big book, like the ubiquitous reference dictionary found in any decent library, or one of those atlases whose covers are as wide and long as a suitcase or trunk.
2. Maybe it has the power to form itself (via illusion magic) into other objects; immaculate chests, small coffers, shipping crates, keepsake boxes, etc.
3. The trap tome can be set to go off by whomever is attuned to it.
4. He or she need only open it to the next blank page, and then imagine something like a chest or box, and will the trap tome to take on the look of what is being imagined.
5. I think the trap tome’s pages should all be mirrors in frames, with a piece of parchment paper between each mirror page. When you open the trap tome up, you get a mirror on the left and a piece of parchment on the right. Turn the parchment page and you see the back of the next mirror frame, which is covered over in a thin sheet of copper.
6. The frame of each mirror is very thin, and is made of hard metal. The corners are reinforced and covered by metal caps. On each cap is a loop and hook so that one mirror page can be attached to its neighbor.
7. The binding for the book includes two pairs of small L-shaped metal legs that run down each side, and whose “feet” touch in the middle of the binding.
8. These can be folded out to stabilize the book when the trap is set, and its owner looks into the exposed mirror with a shape for the book to take on in the forefront of his or her thoughts.
9. When a victim touches the trap tome, the illusion drops and the mirror immediately captures whomever is closest to it, provided that person is looking into the mirror/sees their reflection in it (note to self: check rules for gaze attacks in the 5E Monster Manual). Once this happens the trap tome closes shut.
10. So maybe the trap tome is really like a rectangular shaped box that’s designed to be opened like a chest, its “lid” consisting of all the empty frames whose magical mirrors have captured an unwary victim and transferred the victim’s likeness onto the extra parchment page that can be found between each frame.
11. This process consumes the mirror and “burns” the edge of each loose page into the frame that formerly held the mirror, so each page displaying a victim appears as an extremely lifelike painting on parchment of someone in the throes of surprise (and probably despair), set in a durable metal frame backed by shiny copper.
12. I figure the trap’s maker designed into the trap tome the option to manually remove each page from the binding, so that trapped victims could be put on display all about one’s residence–this is quite the power statement, and warning, to anyone visiting such a home–but the Amnian preferred to hoard his collection and share it with no one but himself.