The charnjibber-trolkin have a Quantum Mirror (for entering parallel worlds).
But I do see your point, hence my tendency for something (Mythic Iron Age Aegyptus or China) that will happily and logically co-exist with the worlds of others to avoid the need for alternatives of the one world. I think it would be more fun to cooperate in one shared world where peoples' specific areas can connect via a portal (Stargates, Mists of Time, Seas of Fate, Star Fairy Silk Road, etc...)
Therefore, in the spirit of cooperation, I have to forgo my laser-headed charnjibber-trolkin (or bind them behind a petrified forest, or something...).