Further Expounding on Canon Divergence / Celestial Headcanon:
While this is a canon divergence I want to incorporate into my interpretation of Quill, this is entirely up to my partners if they would want to develop this in any threads we may have. As I state in Peter's background, the default is that he doesn't know that he still possesses his Celestial powers until post-Endgame threads (unless plotted otherwise in an au).
Even in post-Endgame threads, I will maintain a default that Peter doesn't know he possesses these powers unless we have either plotted otherwise, or the other muse indicates that he has them, or I post a starter call specifically listed and tagged as a ;celestial hc starter call.
I feel passionately about developing this headcanon in threads as a journey of reconciliation of trauma and self-acceptance, as well as a realization of what I believe is a core strength of Peter's, so please feel free to plot or send things my way in this headcanon, or like this post if you're cool with me approaching you with plotting on this!
The reason Peter has avoided even attempting to access his Celestial powers is their connection to Ego (reflecting how he wishes to distance himself utterly from any association with him). Seeing as he was the only one in the galaxy that had these powers, he showed to Peter how he used them, how he wanted them to manifest / what he thought was their most powerful application. He also told Peter it was exclusively connected to the planet to excuse leaving Meredith for long periods / in a desperate attempt to keep him from destroying it because it still was a massive power source for him because he was the planet.
In actuality, Peter’s Celestial powers are connected to the stars, not just primarily a planet. Stars are celestial bodies of pure light, and it’s a direct tie-in to Meredith calling him the light of her life and Star-Lord.
Yondu telling Peter to use his heart to connect with the light within still is true, but how else it expresses itself is discovered and expanded upon. We were shown his loved ones, the connections to the people that matter most, but what’s at the core of so many of those relationships, what is something that makes those memories more vivid for Peter, what has given Peter solace and strength and resiliency through his whole life even when it seems darkest?
Music.
So while the energy source for his powers are the stars, the way they could achieve their full potential is something entirely unique to Peter, something Ego would never have dreamed of. This is the way he can break free from thinking he has Ego’s powers, but rather these are his, a part of him he can accept and embrace.
His powers are not only bursts of light that can take shape, but also sounds that vary in intensity and action based on the song Peter is actively running through his head when accessing them.
He's like Meredith, knowing every word to every song he's heard and that's where a lot of his passion and intelligence shines through. His powers are still tied to his heart, tied to his emotions, but like it has his whole life, music is the way they express themselves fully.
