Does Ardyn's black wing represent his black chocobo?
Recall the black wing Ardyn is sometimes seen carrying. Now, consider this concept art that features Ardyn riding a black chocobo while a crowd showers praise upon him:
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In particular, consider two things this concept art tells us: First, it informs us that some 2000 years ago — before the public was poisoned against him, turned on him, and killed him because of the person the "Izunia" name originally belonged to — Ardyn was glorified. Second, it tells us that he had a black chocobo.
Those things in mind, a question presents itself: Did Ardyn's executioners also execute his chocobo? Is that what Ardyn's wing represents: a lost companion?
Obviously, it's at least in part a reference to Sephiroth from Final Fantasy VII, but it can still serve a function specific to this game and this character, just as so many other references throughout the game are more than Easter Egg alone.
For this fan, it's remarkable how much the notion humanizes Ardyn, who has long since lost his humanity in every sense of speaking. Sure, once one learns that he was scorned by the Crystal and the gods for helping people who were suffering, albeit in a way they didn't approve of, one is already aware that he was given a raw deal. At the least, one is aware of this in an academic sense — and for some of us, that and the lore associated with him is sufficient to make him an interesting character.
Unlike some Final Fantasy villains with unfair treatment in their backstories, we do learn that Ardyn had been doing genuinely good things before betrayal and divine indifference left him abandoned some 2000 years ago. While one may feel an inkling of a sense of injustice for him, there are ever present reminders that he has done inexcusable things to people who had nothing to do with his suffering. Even if the Starscourge is actually influencing his negativity some level, he's still very much aware of what he's doing and why. And it's extremely petty.
Without being able to apply more than just the betrayal he faced to Ardyn's past, it could be difficult to feel for him as much as one would like to. However, looking at that concept art above, as well as the piece depicting him with his arms shackled above his head … picturing him possibly having gone on a long, lonely adventure to save innocent people with just his trusted chocobo for company (maybe he's had this chocobo its whole life, or maybe he met it in the wild during the journey); doing these great things; receiving the gratitude and love of people everywhere like Oracles receive in the present; and then being betrayed by someone trusted — seeing those looks of thanks and adoration twist into repulsion and loathing; watching his beloved companion be dismembered before him; feeling helpless as he is stripped of clothing and dignity, then shackled and perhaps tortured; eventually slipping away into what should have been the release of death only to then become aware of the contamination caking his very soul, rendering it unable to find rest within the literal heart of the now contemptuous world he had tried to save; and finally finding himself back in the realm of the living that had become nothing but pain and horror to him …
Headcanon or not, fanfiction or no — it's the push needed to make Ardyn fully into a fascinating character, simultaneously pitiable and detestable. He needs this so that we can feel the compassion for him that Noctis was able to in the end.
Of course Noct is able to do it: he's the King of Light, the Chosen who will bring the Dawn. He's us as we really would like to imagine we could be. You expect him to pity the villain who has hurt him so much even if we can't — but as the player, you've probably bonded with a chocobo during your travels. For that matter, you've even bonded with a car and experienced heartache at watching it "die."
For this fan at the least, making this connection added a valuable dimension to the character.