Sigilyph (the Avianoid Pokémon) is a relatively rare Psychic/Flying-type Pokémon found among ancient ruins within the Unova and Kalos regions. Incredibly bizarre in appearance and equally strange in terms of behavior, Sigilyph are fascinating creatures that seem to do very little outside of guarding ancient ruins in the wild. Though they might look more like brightly-painted ceramic dolls than living creatures, these strange organisms are certainly no weaklings; dare to attack their territory, and they'll show little mercy as they swoop down and pummel you with their psychic powers!
Much like the members of the Golett family, it is widely believed that Sigilyph are the artificial productions of ancient Unovan civilizations. As with the members of the Baltoy family, it appears that these creatures were originally clay dolls that were brought to life through some unknown means, granting them powerful psychic abilities in the process; unlike the Baltoy family, however, the clay used to construct these creatures is lightweight and actually conducts electricity. This at least gives a physical explanation behind their weakness to electricity while retaining the clay's apparent weakness against cold temperatures. In truth, though, the biggest difference between Sigilyph and the Baltoy family is the fact that Sigilyph can physically fly and not just levitate; this is in no part due to their 'wings', though, as they are wholly inefficient in providing lift. Instead, their ability to fly and therefore their Flying-type nature is a direct product of possessing psychic powers tuned to specifically affect wind currents, allowing them to artificially produce lift and utilize wind-based attacks such as the Gust, Air Cutter and Air Slash attacks. Oddly enough, they are also uniquely different from most other automatons in that they appear to demonstrate bird-like actions and activities, such as flapping their 'wings' and 'perching' on some walls by resting on the small protrusions found on the lower halves of their bodies, despite not resembling birds in any true fashion.
Stranger still, it appears that these artificial creatures still retain memories either individually experienced or brought down through generations from their original time of production. Sigilyph are exclusively found among ancient ruins throughout the Unova and Kalos regions (the latter only due to importation) and are always guarding said ruins from life forms that are deemed to be a threat to the structure's safety, following a set flight pattern that never seems to change; the moment someone or something is detected to have negative intentions towards their 'habitat', Sigilyph will swoop down in great numbers to fight off the invaders with their potent psychic powers and air-based attacks. As such, it seems only logical to believe that Sigilyph were originally designed with the intention of acting as mobile sentries and guardians for ancient palaces while they were still occupied by people, perhaps serving as the first line of defense against oncoming attackers. Why they continue to follow such orders today, however, even when the ruins they are guarding are falling to pieces, is still a relative mystery. It is quite possible that this lone task was psychically engraved within their minds through some method, but in purely scientific terms, there is no current evidence available to support any hypothesis fully. It should be noted, though, that if this duty was actually engraved upon them through their construction and animation, it could explain why the behavior is found in all members of the species with no exception.
Though they might seem too bizarre to be real, Sigilyph are fascinating creatures that demonstrate what the human mind is capable of with the proper resources and intentions. With the right combination of moves to take on a wide variety of positions in battle and as the only Pokémon known to normally possess the unique Wonder Skin Ability naturally, it can certainly be said that Sigilyph are worth training if you're a Psychic or are simply attracted to bizarre creatures. Just be careful to train yours far away from ancient ruins once you've captured it; old habits die hard with these creatures, so you might have some difficulty prying yours away from a site if it appeals to their sense of duty!