It is easy to dismiss the aesthetic sense of the Aether Foundation as an isolated incident, the product of Nihilego manipulating a lone woman. But Nihilego's tentacles reach all the way to Kalos, and both the Kalos League and the world of high fashion have been touched by its influence. The white, flowing dress worn by Kalos' reigning champion and most popular celebrity was not a product of her own imagination, unless you consider her to have merged entirely with the Ultra Beast that has for so long manipulated her actions. Nihilego has been with that woman from the time she was a young trainer, its advice helping her to reach the greatest heights of fame and fortune the region has to offer.
Yet while it is easy to see how Nihilego has influenced these two powerful women, its motivations for doing so are as opaque as its body is clear. Many have noted the stylistic resemblance between the dresses Nihilego's acolytes promote and the Ultra Beast's own body, but the theory that Nihilego can now more easily disguise itself as a young woman and suck out souls with a kiss is difficult to accept, for there is no fashion radical enough to give Nihilego and humans any facial resemblance.
The suggestion that Nihilego wishes to take over the world is admittedly more plausible, but only pushes the question back a level, for it is difficult to percieve any alignment between the Kalos champion and the Aether Foundation president's actions. If we accept that Nihilego indeed wishes to rule the world through a network of white-clad, mind-controlled women, it brings us no closer to understanding why. The Ultra Beasts are strange creatures, and their minds often appear to be even more alien than their bodies...