Introduced all the way back in “The Skinsaw Murders” (that’s Pathfinder #2 for you all keeping track), lyrakien look like pixies or sprites, but are actually butterfly-winged azatas. Unless called by the Improved Familiar Feat, glistenwings will typically be encountered by travelers (making them a good excuse to deliver clues or plot hooks, as the Bestiary 2 notes). They might also be PCs’ first exposure to the plots of the azatas, and are a good way to give the party bard, gnome, or halfling some more screen time during an otherwise combat-heavy adventure.
Listeners passing near Stone Giant Head will be challenged by a chirping disembodied voice. Those who can answer the voice’s three questions will find their way speeded and minor wounds cured. Those who are rude or evil will be left dazed or confused and drawn along a path full of ankle-turning loose scree. Those who sing for the voice will find that Stone Giant Head conceals a pass that will cut travel time along the mountain by a day.
Three groups of lyrakien frequent Birch Vale. The Chapel of the Lost, site of a halfling champion’s death, is always guarded by a band of glistenwings (though never the same one from month to month). The Merry Jugglers juggle acorns and rocks for coins in the market of Ilim, just outside the Temple of the Triumphant Crusader. (This is not a coincidence; the temple serves lawful evil worshippers of a deity of nobility, glory in war, and servants’ submission, and the light-hearted lyrakien are spies.) The blue-winged Midnight Monarchs are a full company of 24 azatas that migrate like their butterfly eponyms (albeit only at night). They are notorious for unleashing their starlight blasts with little provocation.
After the death of his beloved cat familiar in what he swore would be his last quest, the abjurer Cosby Fanshaw fully expected to call another familiar in keeping with his specialization—another cautious cat perhaps, or a toad or hedgehog. Instead he received the surprise of his life: a lyrakien named Aphra who is outgoing, risk-taking, garrulous, and generally everything the abjurer is not. Cosby is stunned to discover himself adventuring again (at Aphra’s urging). She meanwhile has not revealed if what greater purpose, if any, drew her to Cosby. She has also not revealed to anyone but her dryad confidante that she has fallen in love with shy, magic-circle-crafting mage—new emotions that delight and embarrass her to no end.
—Pathfinder 2 58–59 & Pathfinder Bestiary 2 38
The aforementioned Pathfinder issue has more on lyrakien, particularly their connection to Desna.
Lyrakien look like faeries but aren’t. Which raises the whole question of faeries in general. The typical line is that fey (at least the original/elder ones) are somewhat outside the cosmological order—spirits from another age or reality (such as Golarion’s First World), or angels or even Immortals (as suggested in D&D’s Known World setting), who sat out of some great war between the celestial and infernal planes, etc. Often these fey are depicted as not having gods or clerics and are reluctant to enter holy ground or touch holy water. (This may also be what separates fey from elves and gnomes—at some point they entered the cycles of being and mortality in some fashion while the fey stood apart.)
But the nature of fey is also somewhat porous—sometimes fey are also spirits of trees, the land, or gateways; sometimes they have ties to the Elemental Planes; and sometimes mortals can reincarnate as fey when conditions are right. And for every supplement that says the above, the next one that comes out starts listing stats and clerical domains for powers like Rhiannon, Oberon and Titania, Queen Mab, etc.
In my head, I’m keeping them separate, but as usual, you can do whatever you like. If you want lyrakien to be a kind of heavenly fey, or serve as a link tying fey to the azatas, go right ahead.