Shadows and Light

“	The Crimson Spire is a machine, and the Gateway is a part of that machine. The Spire can't function without a human serving as the Soul Conduit… and neither can the Gateway. There has to be a Vessel inside the tower for the Gateway to work.	”
― Nephis to Sunny, Chapter 343 Soul Conduit

Nephis had figured out that the Crimson Spire needs a vessel (Soul Conduit) to make it work which means that only one of them can escape using the gateway.^[1]

Both Nephis and Sunny knew that this day will come, back at the beginning of their journey, Cassie shared with them a terrible vision.^[2]

From the day Sunny had first understood the meaning behind Cassie's vision, he suspected that one day, in order to survive, he would have to kill Nephis. This was the truth he had chosen to hide from, even if it meant losing his mind. The knowledge that one day, they will have to kill the person they care for the most.^[2]

Because he had known that he would have to face Nephis in combat, he had decided to incorporate Saint's methodical style into his technique and trained without rest. He forced himself to accept the terrible truth, that he had refused Nephis' offer to heal him. The same reason he had not tried to learn all of her secret plans, remaining as a hired mercenary, an outsider. He had known that they would be forced to fight each other.^[2]

Sunny was surprised at how strong Nephis was. All that he managed to do was defend and deflect her blows. Even in her exhausted state, she still had an advantage over Sunny. Nephis somehow had grown much stronger than before, even as a sleeper, that it was simply impossible.^[3]

Their violent clash looked furious and morbidly beautiful. Both moved with incredible speed and possessed ferocious strength, were skilled and experienced, and forged into formidable killers through hundreds of deadly battles. But their true combat was invisible to the naked eye. This fight was as much about strategy and insight as it was about physical prowess and technique.^[3]

The scariest thing about Nephis was that she was able to manipulate and dictate her opponent's actions, turning them into her puppet. She was in absolute control of the flow of combat. Her domain was combat, just like shadows were his. Sunny was not a novice either, he was a master of manipulation too. He had enough insight and knew Nephis well enough to, if not deceive her, at least not allow her to lure him into an inescapable trap.^[3]

As they exchange blows, Nephis' wounds that had been partially healed began to seep blood again.^[3] This made his Blood Blossom charm activate to enhance Midnight Shard.^[4]

With the help of the Blood Blossom, Sunny was able to resist Nephis more efficiently even just by a little. But regardless of it, Nephis suddenly abandoned her previous calculated attack pattern, which caught Sunny by surprise. Once again, he was struggling to fight Nephis. But at a critical moment, the Crimson Spire shuddered and the floor beneath their feet suddenly collapsed pulling both of them down.^[4]

The two fought midair while dodging the falling stones. Sunny calculated his fall near the gateway and was about to disappear when Nephis descended upon him which made the process halt as both conduits were cut off from the Crimson Spire, breaking the flow of soul energy. Thus, the Gateway could not function. After they collided and fell out of the ring of the gateway, it shimmered once more.^[5]

As the Crimson Spire slowly starts to collapse, they clashed beneath the dais of the Gateway. Nephis was still too much for him to handle. She was more like a monster than a human. For the first time, Sunny's bag of tricks was empty. So, he did one thing he could think of. A desperate gamble with little chance of success. He incorporated the incomplete Shadow Dance into his technique. He knew her flowing, deadly battle style better than anyone except for Nephis herself. If he had a chance to make that one final step to mastering the first level of Shadow Dance, it was in a fight against her.^[6]

Suddenly, the hidden enchantment of the Midnight Shard, [Unbroken], came into effect. Although the gap of power between him and Changing Star had diminished significantly, he was still losing. But he refused to give up, Sunny had continued to push himself toward mastering the first step of the Shadow Dance.^[7]

As Sunny mirrored her movements, their blades collided, and his style changed slightly. He manifested the essence of Nephis' technique into his own body, mastering the first step of Shadow Dance. At the end of the fight, he was the last one left standing.^[7]

Before Sunny stepped into the gateway, he felt something wrong about their fight. He knew she was somehow able to support two augmentations at the same time and yet, she only used one when fighting Sunny. She then revealed that she created the situation so that Sunny can leave her behind without showing any mercy. And that her goal is still the same, but she thinks that abandoning Sunny is vile and wrong. She didn't want to become the same as those she hates in the process of reaching her goal which makes it pointless.^[8]

Sunny didn't want to abandon Nephis so she was forced to use his True Name to command him to go inside the gateway.^[8]