Sure, I can help improve this chapter. Here's a revised version:
"You seriously don't know?" Ragnarok asked Ruin with a quizzical expression. "Fine, I'll enlighten you, but for you to understand, I need to start from further back."
Ragnarok's face suddenly turned solemn as he began his narration. "I was defeated once by a great celestial. To stop the celestial from killing me, my master struck a deal with Celestalon. He agreed for Celestalon to seal the two of them in a separate realm," Ragnarok's tone turned bitter as he continued. "But Celestalon had other ideas. After he sealed my master in that realm, he didn't hold up his end of the bargain. Instead, he got someone with the ability to transfer souls and transferred mine into a crystal, placing it in the Aracan Temple."
As Ragnarok spoke, Ruin could feel the tangible hatred Ragnarok had for Celestalon. He was too afraid to interject, but his curiosity was piqued. When Ragnarok mentioned the temple, it triggered something in him. Memories of the temple he was in came back vividly. On one of the walls of that dungeon was the word 'Aracan Temple,' and to further confirm his thoughts, he remembered seeing a crystal emerge from the pedestal seconds before he was beheaded.
Ruin was shocked beyond measure as he tried to process what he had just learned. Too shocked to be scared of interrupting Ragnarok, he suddenly voiced his question, "Wait, you're telling me your soul was in that crystal on the pedestal in that crazy killer dungeon?" Ruin shouted in shock.
"Yes, I believe that is how you came to be in possession of me," Ragnarok answered calmly, a complete contrast to Ruin, who was almost convulsing from shock.
"Wait, so your soul transferred from the crystal into my body… does that mean my soul is now in the crystal?" Ruin shouted, fear plastered on his face.
"No, you idiot!" Ragnarok said with a solemn expression, cursing his fate for getting involved with such an idiot. "Let me explain. Celestalon wanted to use my power to take down my master. That's why he transferred my soul into the crystal, so one of his faithful followers could acquire my bloodline. But his plan failed," Ragnarok said with pride oozing out of him. "He underestimated my strength. Anyone who tried acquiring my bloodline ended up being consumed by me, their consciousness lost forever," Ragnarok said proudly as he laughed. "So he decided to wait until my consciousness finally faded away."
"But it's only been a few centuries since then," Ragnarok's tone suddenly turned bloodthirsty as he looked at Ruin. "Which leads me to wonder, what are you doing here? Did that bastard find another way? If so, I won't have any problem killing you," Ragnarok said, his bloodlust filling the space, assuring Ruin he was not bluffing.
I hope this helps! Let me know if you need any more adjustments or further assistance.