Maybe rather than giving them the historical items, you give them a scavenger hunt of categories which they pick the details for themselves, and then give them the challenge? Like a Mad Lib, almost. "Pick a world leader of the last 1000 years, an insect, an Oscar-winning Best Picture, one deity from an established pantheon, the most famous piece of art you can think of, and a type of weapon."

(Maybe you could use focused-but-subjective terms like "the best", "the worst", "the most famous" for all the categories, so that there is opinionated variety among the participants but not totally random divergence.)

Also: I fail to see the point in making anyone a paranoid conspiracy theorist "temporarily". ALL OR NOTHING, BABY!