Pixilate is Sylveon's Hidden Ability.
Hidden Abilities can be found from hordes, the obsolete Dream World, and the Friend Safari. As mentioned, the Dream World is obsolete, Sylveon or Eevee can't be found in hordes, so that leaves the Friend Safari.
Eevee, Sylveon's evolution, can be found in the Friend Safari, but it strictly depends on what your friend codes. So, it really depends on you searching in the depths of the GTS, or if your lucky, a friend's safari, for a Hidden Ability Eevee. Unfortunately, there's no other good way of finding one. Sorry. :(
Once you do find one, simply evolve it and boom! Instant Pixilate Sylveon.
Hope I helped. :)
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