SPOILERS FOR ENTIRE SERIES/BLOGS

Let me start this off by saying, I'm sure bits and pieces of what I'm about to theorize have been mentioned or thought of many times before. I am not saying that everything I have to say is original. But I believe some key parts are, and the whole thing together, is definitely worth talking and thinking about. This will be long, but I will have a TL;DR at the bottom :D...

Okay, let's start this off with this truth. Rachel is the protagonist(female at least) of this story. She may or may not be the heroine, depending on whether you look at it in the lense of SIU on his blog or the characters of the story themselves.

The female protagonist is Rachel. She's more like a "female protagonist" than a "heroine." As for the heroine, She will appear in the future. Baam, surprisingly, will cause many women to cry. -SIU

It's important to note the difference between protagonist and hero(ine) per vocabulary.com

The difference is in their Greek roots — the word hero meant "demigod" and a protagonist meant the first person to address the chorus in a Greek drama, also known as the main character.

Basically, the hero, main character or not, is someone extraordinarily special who accomplishes good deeds. A protagonist is someone normal or hero through which the story is told by/for. Basically, Headon-nim and Hwa Ryun are using the term "heroine" as bait in my opinion. Or from her position as protagonist she is the heroine of her story. But she isn't very special. More on this in a bit.

How is she not the antagonist? Well, this theory rests on the idea that Baam is the Prince of Zahard. There isn't much evidence on this, but two big things give it credence. 1. At the end of the Workshop Battle, Po Bidau Gustang was asked "who was the 'real' Zahard's Prince that will take the Tower's last test?". In the blogs it is said that many people wait on the Prince of Zahard. Part 2 is called "Return of The Prince". 2. Where Baam grew up, he had the symbol of the King watching him. It's possible that Ja Wangnan is the "real" prince. Hence, the askers question. Which one is it? But I believe he's a fake. The Ten Families' greatest mistake.

How come out of all the ten families having children and a legacy, naturally, only Zahard has adopted children. Why is that? This is pure conjecture, but I believe he was given a prophecy, either when entering the Tower, at the moment of "Revolution" in the Train, or sometime thereafter (most likely with Phantamium) something like "A Prince of Zahard will overthrow you". Prophecy and fate are already big things in this story, just look at Guides.

If true, this would go to speak as to why Zahard has never had naturally born children (don't want to risk it), and his princesses are forbidden from relations(Would be a Prince of Zahard as much as Anak is a Princess). So Ja Wangnan was a mistake, probably through a male version of the princess process. But Baam is the true prince, probably biological, or at least something done explicitly through Zahard. And Zahard has been actively Against Baam from the moment he entered the Tower. Through the rice ball in season one aka the R.E.D. and most explicitly, when in chapter 78 Yu Han Sung tells someone over the phone that the "Jahad(Zahard but not as cool) family will believe he's dead, no problems" it was important that he was dead and reborn. In season 2 you see various people surprised he's back from the dead, including Yuri, I believe, showing that bait was took.

So Zahard knew of a prophecy. Took steps against it. But had his symbol over Baam in the cave. Why let him live, knowingly, to the point where the second he enters the tower you're sending people after him, and you'd keep after him to the point where FUG makes you believe he's dead. And it's not just that he's an irregular. If that was the case, and Baam is the prince, but you have no prophecy of your prince overthrowing you, why not just keep him in the Tower, raise him as your heir, and within the laws of the Tower have him unable to kill you? He was still afraid of the prophecy anyways, The prophecy made it self-fulfilling. Making him an outsider, banishing him away, ironically, gave him the chance to be overthrown. Which brings me to the reason why he banished instead of killed. For whatever reason, Zahard cannot find it within himself to kill his own children. Look at Eurasia Enne Zahard, a princess who went crazy, killed many other princesses and royal guard, and still, Zahard could only seal her. That plus any lingering feelings with Zahard and Baam's Biological mother(if he had one) led Zahard to banish him too, only if he came back and thus became a threat, would he nip him in the bud(and failed).

So Baam and Rachel have their thing and then she leaves because she's haunted by the stars, more on that later. Soon, Rachel is the pawn of two groups/people. Well, they're actually all using each other. First, Headon-nim. Headon-nim manipulated and abused the heck out of her. But then he offered her a deal. To become the Heroine of the story and be allowed to go up. In this theory, the deal is, she must not be with the Boy. She must continually be away from him as she is the reason he climbs the tower. Baam literally cannot comprehend going up there for anything else. As much as Rachel is haunted by her stars, Baam is haunted by his (Rachel). Why does Headon-Nim want Baam to rise through the tower, to the point of working with FUG. He's a guardian of the tower, some say, the true ruler of the tower. And what is the purpose of the tower? Rachel says, that once, a man so loved the stars that he built a tower to reach the stars. The Tower of God. Wherein everything lies at the top. The Guardians, then, are beings who test only those worthy to reach the top. But on the other hand, they exist so that someone may fulfill the Tower's purpose and reach it. I believe when Zahard first entered the tower, it was his destiny to reach the top. But I believe he chose a different path. The path of the King. Of the conqueror. The first power Baam saw in the Rice Pot. The one he denied. And that power was not worthy of the top. So he too, met his wall. And so the Tower and it's Guardians had to seek balance. Another Path. The 'real' prince, destined to take the Tower's Final test. Headon-nim is using her to get the Prince to the top where he belongs. A reluctant hero indeed. And Headon-nim knows Zahard, the king, will never allow someone to rule over him. It is against his nature. So the King must be overthrown. Hence, working with FUG. Yu Han Sung is told everything by Headon-Nim, and aside from her first spear-bearer, says that everything will be provided for her that she needs to go up.

How is she not the Antagonist? She didn't try to kill Baam. There is literally no way she actually wanted him to die. She was working with FUG. With Hwa Ryun and Yu Han Sung, whose whole goal was to take Baam, make him "dead" and rebirth him underneath them. He had to "die" there. Not actually die. The name Baam, had to be erased. And she had to be seperated from him for him to Climb and grow and become what he must. She followed Headon-nim's deal first, and FUG's, second. But this was not her first plan. For her, she never wanted Baam to know that she was Rachel. She worked extremely hard to be Michelle Light. Why do that, if your plan all along is to betray him. The reason is, her Pact with Headon-nim is absolute. She cannot be with him, she cannot be anything but the reason he climbs to get her. He must never have the star. He must continually ache to grasp it. But the relationship with FUG is only one of convenience. So, even while being affiliated with FUG from the beginning, if Baam doesn't know she's Rachel, and isn't with her, he still has to chase after her, or Michelle, or whatever he thinks to get her. She doesn't have to follow FUG. She can just let Headon-Nim carry out his promise. That's why she pleads with Khun. But she failed. He did find out. And so, the plan has to change. She has to go all in with FUG. To walk the path she chose as the "Heroine". But she is never happy with it. Every time you see her face when she's talking with Baam, you see, flashes. Of pain, guilt, confliction. And then she'll turn stonefaced and do what she must to see the stars. But she doesn't hate him, nor does she particularly enjoy her path. She's instead "tired" of the path and afraid of it. In reality she sees that Baam is getting lots of friends and she's still alone. Just a bad, lying little girl. But not an antagonist. Rather, very much, a protagonist, the most human character of all, with an all consuming dream. Much like Baam.

Finally, who is Rachel? Why does she feel Like Baam has stolen everything from her. Why is she the only one who calls the towers Guardians "Fae". Why does she know the story of the stars that even Khun was confused and laughed about. I believe she is a descendant of the one who built the Tower. It would explain why she's so crazy about stars and fearful of the night. It would explain why she's so jealous that Baam, son of Zahard, has all this talent, gift, greatness, and she has nothing. And it adds a bit of a star-crossed lovers feel between these two great lines. It's also why she would be able to know so much about the Tower from the outside, and be able to go between the cave and the gate herself. And headon-nim played her. The Tower only opens for what it needs. The Tower didn't open for her, but for the boy. Half-Truths. They both are irregular. And the Tower needs both of them. But only to get the promised prince to pass the last test and fulfill the Tower's purpose.

But she struggles against fate. Hence why she is going to get her own "thorn". Why the word "thorn". That's only been used in the context of a weapon to kill Zahard. Look at how she took Hoaquin, for example, making him her sword. Why not get more swords, or a shield, or a leg, or a spear, or any other item. No. She wants a thorn. She is struggling, because, she has to steal everything to get even a little bit of her dream. She knows that as an irregular, she too can kill the king, and with a Thorn, if she's able to kill Zahard, she can move up, and see the stars herself. She is unable to rely on Baam. She must take what she needs to move forward herself.

I think, by the time we get up there. She'll be killed by Zahard. And Baam will fulfill the prophecy. But will not become a King like him. He will head to the top. Both for Rachel's dream, for her sake, but mostly because, "Everything is at the top". The only way he could possibly see her alive again, is by reaching the top. If/when she dies. He will seek his star, just as he does now, with even more ferocity. In the end, they both do, and will, want the same things.

TL;DR 1. Baam is the Real Prince of Zahard 2. Rachel never tried to Physically kill Baam 3. FUG, Headon-nim, Rachel, are all working to get Baam to keep moving up. 4. Rachel still wants to get to the top for her own reasons. 5. Baam will kill Zahard. 6. Baam and Rachel will be the ones to clear the tower, in one shape or form.

Many thanks to SIU, Tower of God wiki, Webtoons, and you the reader.

I'm sure there's more I'll add or expand about later, but my fingers hurt now :D... Let me know what you think!