u/Lady-Death-of-Dusk

I thought HOFAS made it obvious that Nesta is Starborn, while simultaneously shutting down any possible theories that Az might be, but I've seen people claiming the opposite. So, let's explore the evidence.

Starborn Tattoo: Nesta had the eight-pointed star tattoo on her back. Az did not. We know the eight-pointed star tattoo was chosen by the magic when Nesta made her bargain with Cassian, and we know it's the symbol of the Starborn because Nesta told Bryce that it looked just like her scar, which is also the same eight-pointed star in the Prison chamber. Az could have easily been the one with this tattoo in ACOSF - he could have made a bargain with Cassian where the magic chose that design - but yet he wasn't. Nesta is the only ACOTAR character who had the Starborn logo tattooed on her.

Starborn Chamber: Nesta found the chamber in the Prison, whereas Az, in his 500 years, never knew that it existed. Bryce mentioned in HOFAS that someone could have only found the chamber if their starlight guided them to it. This proves that Nesta has starlight - the magic of the Starborn - as Nesta is the only ACOTAR character to find the Starborn chamber.

Canonically, Nesta and Bryce are the only characters to be able to enter the chamber. Az could only enter when Nesta opened up the wards to allow him in. This, in and of itself, proves that Az isn't Starborn because if he was then he could have entered without Nesta's assistance. Nesta is the only ACOTAR character to be able to enter the Starborn chamber.

Dread Trove: Nesta found, can summon, wield, and control the Harp and the rest of the Dread Trove, whereas Az cannot. I mention the Harp specifically because Bryce said that the Harp was left for a Starborn to find. The last person that used the Harp, prior to Nesta, was Silene and the last person to wield the Horn, prior to Bryce, was Helena, which supports the theory that Nesta is a descendant of Queen Theia and Fionn. Even though ACOSF said that Made people can wield the Trove, that doesn't seem to be the case since Theia, Helena, and Silene wielded them and they're not Made. Plus, CC said that the Starborn, with their starlight channeled into the Trove, can bring the objects to life. Nesta is the only ACOTAR character who found, can summon, wield, and control the Dread Trove. Queen Briallyn wielded the Crown (to an extent) because of Koschei, but the Crown seemed to choose Nesta over Briallyn since it did nothing to protect the queen from being UnMade.

Gwydion and Truth-Teller: We know both blades answer to the Starborn bloodline by emanating with magic for them and them alone. Neither blade emanated with magic for Az, proving yet again that he is not Starborn. Simultaneously, SJM made sure that Nesta touched neither blade at the same time. Nesta wielded Ataraxia in the tunnels, Bryce laid Truth-Teller on the table, and only handed Nesta Gwydion right before she shut the portal. The lengths SJM went to to make sure we wouldn't have confirmation of Nesta being Starborn just further proves that Nesta is. SJM could have easily shut down any potential theories by having Nesta touch both blades and them not emanating with magic.

Both blades also left Az's hands when Bryce beckoned for them because, once again, she's Starborn and he is not, and the blades always answer the call of a Starborn.

Az is definitely something - a descendent of Enalius perhaps? - but he's not Starborn. All signs point towards Nesta being Starborn, either the descendent of Queen Theia on Silene's side or made Starborn via the Mother while she was in the Cauldron.

I really feel like we're gearing up for an Az/Cass conflict next book.

Az is so lonely and desperate for a mate, and Cass has everything Az could want: a mate who loves him so fiercely that she risked the perils of the Bog of Oorid to find him, a mate who has saved his life on multiple occasions, a mate who will always have his back and will always defend and protect him. But Cass is so oblivious to his mate that he's letting her wither away because he's too angry to pay attention to Nesta's negative emotional state.

Az has a deep love, respect, and admiration for Nesta. She's so much of a badass, and he's so proud of her, that he bragged about her badassery to Bryce, a complete stranger from another world. I know he's upset with her at the moment, but as soon as he gets Truth-Teller back and finds out that Nesta helped save Midgard and, by extension, Prythian, I really feel like he's going to take a good, hard look at her and notice how far she's fallen back into that pit of despair, and I don't think he's going to be too happy with his brother.

It's a mate's job to not only protect their mate, but pay attention to their well-being, and Cassian spectacularly failed on both fronts. I really see Az calling him out for it, and the two of them having some tough conversations about Cassian needing to step up and take Nesta's side. Because if Az had a mate who loved him the way Nesta loves Cass, he wouldn't hesitate to side with her and he most certainly wouldn't ignore her emotional state and let her get as vacant as Nesta has become.

Yes, exactly. Hence the point of the mating bond being the most valuable bond in their world (even surpassing that of husband and wife).

Every time Cassian sides with Rhys over Nesta, he diminishes the importance of the mating bond being the most valuable bond in their world.

"Cassian has only known Nesta for two years!"

He only knew Feyre for two months when he sided with her against Rhys.

Lucien had only seen Elain for five minutes when he left Tamlin for her.

And let's be honest, Rhys would never side with Cassian against Feyre, who he's only known for two years.

If Cassian wants to be conflicted about who to side with then Nesta should still be conflicted about whether or not to accept the mating bond. If Cassian wanted Nesta to accept the mating bond, promise him forever, and be fully devoted and loyal to him and him alone then he owes her the same loyalty and devotion. He can't demand more from her than he's willing to give.

Cassian sided with Rhys against Nesta, and his mate went on to help save Midgard and, by extension, Prythian. Cassian chose Rhys, and he chose wrong.