Quote from GCRust
To me, Void Ages are Prison Books. But if you want to not be a jerk in multiplayer (As there really is no escape from a Void Age for a player, even if another player linked in with a book), I'd say Monster Grinder ages (Eternal Dark Ages, essentially) would be Prison Books.
The "problem" is, even if you want to try to sucker people into your Trap Age, there's no real way to do it as folks will just read the description of the Age and realize it is "Booby Trapped".
Unless they just blindly link to any book in your Library, in which case they deserve what they get.
i was thinking about this earlier, and i was thinking why not let void ages not be a symbol, but rather the ultimate form of instability? for example, choosing a single biome world modifier and choosing 2 different biomes makes a world unstable, and decay will form. but what if you just went crazy with the instability? add 3 biome modifiers, 4 biomes, 2 weather modifiers...not only would this solve some of the problems brought up earlier with the void age symbol, but it would also keep void ages achievable, as well as throwing in an interesting mechanic of allowing discreet linking books to be made. of course, it could still be determined whether or not the book may be a void age to a good writer, but to anyone who blindly links, there wont be any notification, and there wouldn't be any single symbol to search out.