Challenging the Leviathan, a beast several millennia old, of which only a few existed on all of the Calysta continent, with just two people, one of them not even one of the most powerful in the continent, was a foolish idea, no matter how one looked at it.

Even Noah was vaguely aware of this. Vaguely. The reason he was doing this at the moment was not because of a random idea he had in his sleep. No, he had a proper reason for challenging a foe stronger than even the false heavenly kings he had once challenged, which took three of his party members who were also high up in the hierarchy of strength on the Calysta continent.

This reason had to do with how he would get stronger from this point onwards. A few days ago, when Noah had just woken up from his three-day sleep, he had briefly theorised about a method he could make use of to get stronger. At the time, he had not expanded upon the thought, distracted by Ariel's sudden marriage proposal. But over the past few days, swamped in all sorts of customs for a marriage for a noble and successorship of a title, he had plenty of time to let his mind sit on the idea while he waited to greet nobles who arrived from all sorts of territories.

Magic. On the Calysta continent, magic is operated by a system of magic circles. The more advanced the spell, the more mana it took, while also generally being more destructive. Mages required two things to cast a higher circle spell—the corresponding number of spirit casts and the use of the mana flow of the spell by the spirit.

A spirit cast was a spirit moving mana around according to the flow of mana used by a spell on top of a mana node or an external object that acted as a mana node. If one used the First Circle - Ice Needle spell, the spirit of a person would move mana according to the mana flow necessary to do so, casting the spell. This was the reason why everyone on the Calysta continent could cast First Circle magic. They were incredibly simple, useful, and required so little mana to cast. Spells like the First Circle - Clean spells were indispensable, and they would only exhaust the spirit of the average person by a quarter.

However, higher-circle magic was where it got more complicated. The most commonly employed method was to build another spirit, overlay it over the first spirit, then merge them such that they would function together. The second spirit could be filled with mana and consequently increase their magic pool. Mages that wanted to reach the peak would carefully build their second spirit so that it could be as large as possible without collapsing.

When one casts second circle magic, they would need to use both spirits to cast different parts of the spell, as second circle magic requires two different mana flows. The two spirits would cast two different spirit casts that would work together to produce the spell.

Archmage Elowyn, the best in Eldoria, was an example of a peak archmage. She had large spirits for all second to ninth spirits, thus having the mana pool of several archmages.

There were other things that defined a good mage, but this was believed by most to be the most important factor.

Powerful magic from humans needed such techniques to cast powerful magic, but different species did not do the same. They relied on spell intricacy to cast incredibly efficient spells—destructive yet highly mana-efficient. It was like how a car engine used less oil to move a car, rather than if oil was just spit out a car at high velocity to move it.

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When a different species cast different types of magic, they did this by using the mana flow engraved in their soul. When mana was sent into the soul, it would act like water poured into a tube, where the mana flowed by itself with no action from the caster. This mana flow was usually incredibly complex and impossible to employ without the engraving.

When Noah transformed, his soul did not transform, but rather, the engravings of these other species would be temporarily engraved on his soul until he transformed back.

Technically, a species was defined by the engravings on its soul. This is why each Hero was technically a different species entirely. They had skills engraved in their souls, unlike the usual human, who had a clean slate of a soul.

But this was not how magic used to be performed on the Calysta continent. Historically, rather than build new spirits, mages used to tear their spirit apart. This way, one spirit became two, that could work in tandem to produce higher circle magic. The tear where the spirit would mend itself together would form a sort of scar, which had a slight volume to it. The sum of the volume of the spirit that had been fragmented and the scar would be greater than the original spirit, thus increasing mana capacity, even if not to the extent of the spirit building technique. These scars separated the spirit such that separated parts were technically different spirits, while still allowing it to work together.

If modern mages used mana veins engraved in their spirit to cast magic, these ancient archmages who tore their spirit to use higher circle magic transported mana through these scars. These scars were much larger than mana veins; this was more commonly known as a mana canyon, and vastly increased the efficiency and speed of mana use by the user.

Imagine a small circular piece of plastic with a hole in the centre, much like a CD disk. When one poured water on the plastic, they would have one stream of water. If one overlaid or stacked nine of these plastic discs on each other with gaps in between, they would be able to get the water to flow through the bottom disc while also getting the water to flow in all sorts of weird ways if they chose to misalign the nine discs, as long as they ensured the water didn't spill out by building walls around the discs.

Now, imagine just one disc with nine large holes poked in it rather than one smaller one. They would be able to get a much larger volume of water through the discs.

This was what Noah intended to do. By splitting his spirit apart, he would be able to get each part of his torn spirit to execute the mana flow of mimicry engraved in his soul simultaneously, rather than one at a time, if he chose to build and overlay multiple spirits instead. Like water flowing through discs, nine streams of water by splitting his spirit, rather than just one if he overlaid multiple.

The only problem was that spirit-splitting wasn't all that easy. New spirits were made by careful condensation of mana, a slow process that guaranteed success if done well. Splitting it was done by constructing a mana blade within one's own spirit, then using it to tear it apart.

The construction and use of this mana blade required delicate mana control, which Noah didn't have. Noah thus had to use the inferior method—recklessly using mana to its limit and straining it beyond its limit in hopes that it would tear.

This actually would have happened to Emma if she had continued to funnel mana she didn't have without letting herself faint once she was safe. The atmospheric mana that would have rushed into her had her spirit actually torn instead of only being strained to its limits would have prevented her disaster.

Spirit splitting using this method couldn't just be performed by expelling all their mana and more in a safe environment. No, the threat of death needed to be present. Only then, would a person push themselves to their limits, without allowing themselves to faint, could they be placed under sufficient stress that their spirit tore.

But what kind of beast could place Noah under the threat of death so easily?

'The Leviathan would be one of them, I reckon.'

With a wild grin, Noah stood with one leg on the bow of the flimsy boat he and his wife were on, undaunted by the furious wind and storm fettering him or the tumultuous waves that threatened to throw him off. His wife sat on that same bow, her red hair in a wet ponytail, jumping about according to the movements of the waves. Behind them, most of the boat was occupied by a small hill of…white rope?

And in front of them was a proud leviathan, a colossal green sea serpent fully visible even in the furious storm, over half a kilometre long.

"Finally, a worthy foe! Our battle will be legendary!"

"What? I can't hear you over the storm!"

"Nothing; don't mind it!"