The Grand Empress has said, on occasion, that she rules over a billion worlds. This humble scholar cannot believe that number is even remotely true, as it begins to violate the Rule of Universal Finity. If there were anywhere close to that number of worlds, then many of them would possess some level of traveler science, and we'd be overrun with travelers. As it is, dimensional travel is fairly rare, only common in certain corners of the cosmoverse. That being said, we have no way of really knowing how many worlds the Grand Empress does, in fact, reign over. Keeping this information secret may be the real reason behind her outrageous claims!