He started to dislike the first sage when he was approached by the racial council and offered a deal to give up all his responsibility and right to Soverick to them. He had no choice but to agree. He was an Origin god and also a battle sage monkey. He couldn't fight back or refuse. The smart decision was to agree to the deal. He even benefited greatly from it. But that doesn't mean he is alright with it.
The thing he hates the most is oppression. He will never submit to oppression. He will keep on fighting even against the heavens. The other thing that he hates is disappointing the hopes and dreams of people that rely on him.
He didn't give up even when he was near death during the war against the Vipers. He continued to fight. He was willing to give up what little life he had just so that the hopes and dreams of the battle sage monkeys will not be let down.
Hadrick helped and believed in his so he risked his life in the tower of heaven and stood up against heavenly tribulation for his beloved. His descendants rely on him so he was willing to sacrifice his potential as a world god to create a safe haven for them for when the universe ends.
But then the first sage came along and combined the two things he hated the most into a deal. The first sage asked him to betray one of his descendants. He had to give up that descendant because the first sage is stronger than him. He did it for the other descendants. If not for that responsibility, he would have refused and fought a world god as an Origin god.
He couldn't refuse back them. The first sage would have had his way no matter what. His family is in the plane and they might suffer for his rejection. So he just went along with it. Then Soverick died and was replaced by Salvini. He might have let it go if it was someone from another bloodline that replaced Soverick. But it was someone from the same bloodline as the first sage. It is as if the first sage believes that his own bloodline is better than the bloodline of heavenly punishment.
Soverick doesn't have his bloodline, but he is still a descendant of the Ghastorix family. Soverick helped the first sage to gain a lot of wealth and was killed for it. Ghastorix's love for his race and his respect for the first sage could not stop him from hating the first sage anymore.
He decided not to kill Salvini because of her new title and because she helped him keep Hadrick safe. But her ancestor is going to pay for his crime. Then the keeper of secrets came to him and everything clicked together to result in him coming here.
He is not so weak anymore. He is a world god now. That means he has the right to challenge the first sage. He planned to do so after his world stabilizes. But he knows he still can't beat the first sage. At least not alone. Fortunately for him, the keeper of secrets allied with him. If he gains one more ally, then he is confident in killing the first sage at least once.
Ghastorix spoke solemnly, "I will fight the first sage. I will fight him for my descendant that was killed unjustly and for myself that was made to concede. I will always fight against oppression. Therefore, I, Lightning Of Heavenly Punishment swear upon my world that I am not working with the first sage in any way. I swear it that I won't betray you. I swear it that I will not give up until the first sage dies at least once."
The serpentine world god was satisfied with their Oaths. He let down his guard a little bit. In fact, he became happy. He has tried to find allies to help him fight the first sage but all the world gods it contacted refused. Now it has received helpers.
"Welcome, welcome." He said to them happily.
Then he asked them, "What is your plan?"
They began to discuss how they will bring death to the first sage. The keeper of secrets is the major planner. She is also the foundation of their cooperation. After all, she is the one that brought all three of them together. One might call her a mastermind.
She knew about Ghastorix's hatred for the first sage. So she told him about the bet, Soverick's part to play in it, his death, and how much the first sage gained from it. But she didn't tell him that Soverick is still alive. Ghastorix doesn't suspect it either. He doesn't know what Soverick really is.
She is using the hatred of the Ghastorix and the serpentine world god to further her schemes against the first sage. They planned together for a long time then they went their separate ways after swearing an oath to cooperate with each other.
The keeper of secrets chuckled and thought to herself, "Now I know how that cunning snake feels when he toys with people. All these brainless idiots who have power but lack sight are tools to be molded to ones wish."
The serpentine world god thinks that he has escaped the situation of being toyed around. He is wrong. One might say that he has just jumped from a frying pan to fire. He is the strongest one among the three of them but he is the one that is mostly likely to suffer the most. Who knows if he will suffer more than what he has already suffered because of this cooperation to deal with the first sage.
He is the strongest one but he is just the collateral damage of the clash between the first sage and the keeper of secrets. His strength doesn't make him a player. He is still a pawn. It is just as the first sage said to Soverick, strength isn't everything needed to control one's fate. The keeper of secrets is able to use her advantage in information and knowledge to manipulate two world gods for her purpose.