Fate/Tower of God - Climbing the Tower as/with Mordred (fanfic)

First Floor of the Tower, Headon's Floor.

Sensing the changes in Shinsoo, the Guardian of the First Floor of the Tower, Headon, slightly shook in surprise and excitement at this familiar sensation.

It was a sensation that he only felt a few times in his life, but one that he could never forget.

'Another one opened the door.'

Expecting the arrival of a new Irregular in advance, Headon quickly hid himself in the Shinsoo to observe the new arrival for a while, his eyes glinting with curiosity. Unlike the earlier boy, which was long prophesied, the appearance of this Irregular wasn't something that he had foreseen at all.

Soon after Headon hid himself, a person's body materialized in the cavern.

Headon looked at the newcomer with curiosity as his mouth slit slowly split open to reveal one of his eyes.

At a glance, the new Irregular was a young man that looked to be in his mid to late teens, but Headon knew that looks can be deceiving.

It was difficult for Headon to judge, as a member of a completely different species altogether, but the young man seemed rather 'good-looking' by human standards.

Apart from a 'smooth' and 'good-looking' face, the young man's characteristic features included bright red eyes and long light-blonde hair. His red eyes were bright crimson like rubies, making him look more noble rather than evil, while hair was bound into a wild half-ponytail at the back, with meticulous braids at the sides of his head, wild bangs that covered most of his forehead and longer side-bangs framing his face; this half-elegant half-wild hairstyle made him look both heroic and also noble.

The red eyes paired with blonde hair made the Guardian notice the similarity to the current 'King of the Tower'; although Jahad's real eyes are not red but golden, he does wear a red eye mask at all times.

'How amusing…'

However, the most unusual and eye-catching aspect of the new Irregular's appearance by far was certainly a bulky full-plate armor that covered his entire body apart from the head, as well as the sword in his hand.

The sword, in particular, attracted Headon's attention, as it emitted a fascinating and dangerous aura similar to that of the most special weapons in the Tower.

Altogether, the new Irregular gave off the feeling of a young armored knight of noble origins.

'How interesting. Like a knight from a legend. A sword to cut the greedy king's neck, perhaps? Or is it a new 'king'?' Headon secretly snickered as his curiosity got the best of him, making him reveal a row of razor-sharp teeth in anticipation for the future.

…

[Isaac's POV.]

Isaac observed his changed body with a solemn expression.

It had only been a while ago that his body experienced a change as he became more similar to his Servant Mordred. He had only momentarily appeared in a dark cave before being teleported here, and didn't get used to it just yet.

Firstly, he seemed to have an appearance that closely resembled his Servant, and even his hair became longer, with the only exception that he was a man.

His hair and skin had both become smoother. He wore Mordred's armor as well, and in his hand was the broad-bladed longsword Clarent.

Most notably, he felt filled with strength, energy and vigor like never before.

The change of his appearance seemed to be positive, but Isaac was most in awe by this new feeling of power.

He could perceive his surroundings in great detail, he felt as if he could jump up tens of meters high and crush rocks in his grip if he only tried, and if he only concentrated, it felt as if the time around him flew in slow motion.

'Amazing…'

As a Magus, Isaac always wanted to attain great powers for himself. 

Although he was self-taught when it came to Mage craft, had no family support and no inheritance, he was a good talent, was smart and always worked hard.

It was only unfortunate that the world and the period of time that he was born in did not allow the emergence of powerful Magi.

However, one day he received an opportunity. Because he was a Magus, he became a part of a Holy Grail War by chance.

Thanks to wit and luck, he managed to become the final winner among the seven Masters, but at the cost of his Servant Mordred.

At the end, he took the Holy Grail into his hands, the famed wish-granting device, and eventually made his wish…

Being the greedy person that he was, he tried to make the best of this opportunity. Rather than wishing for a single thing, he wanted to realize all of his dreams, ideals and wishes, and to attain eternal life and God-like powers.

That's why, after consideration, he made a complex multi-layered wish that would allow him to achieve all that he wanted.

As a result, he appeared in this new world and in his new body that was filled with strength and potential.

As for his Servant Mordred, she was also resurrected and her spirit took refuge in his sword; Isaac assumed it to be a part of his wish of interesting powers and a companion.

At this moment, from the moment that the two were swallowed by a beam of light from below and appeared in this second cavern with murals, Mordred's voice continued sounding out in Isaac's head:

[What is this place?]

[Hey, Master, look! They have a cool ceiling! It's like the night sky!]

[Oi, Master, are you listening? Hey, I'm here!]

"Yes, yes, I know you're there," Isaac finally said, pulling his hand back from his cheek.

[Okay. It's amusing how you look similar to me, but stop touching yourself, you narcissist. Haha!]

Isaac smiled back when he heard that laughter. At first he felt annoyed; he felt annoyed at being nagged when he heard his voice, but he felt very glad to have Mordred back; in his life, Mordred was probably the only person that he so far considered a friend.

At that moment, responding to Isaac's words, a strange chuckle suddenly sounded out from somewhere. "Hehe, I didn't expect you to have such a high level of vigilance. Is that because of your weapon?"

Isaac looked over and saw a humanoid rabbit with a staff in his hand appear from within the darkness. The rabbit had white skin and two long, pointy ears that creased back from its head. Its mouth slid traveled across the entire oval-shaped face, as if it had on a permanent smile, yet he had no visible eyes.

This sudden appearance of the monster slightly startled Isaac, making his armored hands reflexively ball into fists.

Simultaneously, his instincts screamed at him to be wary of the being in front of him, as he was vastly inferior in strength.

[Master, watch out, this guy's scary!] Mordred also warned.

"Don't worry, I won't hurt you," the Rabbit added . He spun around a stick with two balls at the ends once and added, "My name is Headon, Guardian of the lowest floor of the Tower. What is your name?"

'... Headon?' Isaac raised his eyebrows and was surprised when he heard that name.

Hearing the monster's introduction, together with the appearance of this entire cavern, he could not help but recall a vague image from a certain fictional work that he read before. It was a manhwa called the 'Tower of God' - he remembered it rather well because of the simple name.

'As a result of my wish, I end up in the 'Tower of God'? Is that where I was supposed to realize my wishes?' Isaac thought.

As Isaac thought of this matter, Headon soon spoke again: "You can understand my words, can you?"

"... Yes, I can understand you. My name is Isaac."

"Isaac… Is that all? You seem like someone from a distinguished family," Headon said politely, inquiring further.

Isaac felt as if the Guardian tried to gain more information on him. He pondered for a while, then said, "Ainsworth, I'm Isaac Ainsworth."

In truth, he only had a faint relation to the Ainsworth family. The surname that he was born with was different.

However, he was aware that he could take up any name that he wanted when entering the Tower, so he decided on Ainsworth.

"Isaac Ainsworth… It's a family name that's a bit hard on the tongue, but very well. I welcome you to the Tower, Mr. Isaac. How come you ended up in this place?"

Observing the humanoid monster's unreadable expression, Isaac thought for a moment, then smiled and said, "Well, I just wanted to go on an adventure. And then… I was suddenly here."

For this Headon, Isaac always had bad feelings about him in the story. It felt as if Headon had his hands in everything that happens in the tower, mostly in everything *bad* that happens in the tower, as he secretly manipulated things from the shadows.

The less that Headon knew about him, the better. Isaac's true intentions, which was to become powerful, immortal and fulfill his desires could be left to himself; he's just an adventurer!

In turn, Headon's expression did not change and remained unreadable. He replied, "So it was like that. Now then, since you are already here… Do you want to go up the Tower?"

At this question, Isaac slightly gulped in excitement.

At that moment, Headon looked up as he raised his staff up, pointing it at the mysterious starry ceiling that seemed to have no end, and continued, "The Tower is a place where dreams and wishes come true. No matter what you desire, whether it is wealth, glory, power, immortality, beauties, happiness, adventures or excitement… You can find it all as long as you go up the Tower! The Tower is such a place."

Isaac pursed his lips as he tried to conceal the excitement within his heart at those words.

Wasn't this exactly what he wanted? A fantasy world, a place where he could gain great powers and fulfill his desires?

Headon turned to look back at Isaac and continued, "But do keep in mind that it is a risky and painful journey to embark on, young man."

Isaac didn't care as he smirked, replying, "It doesn't matter. I really want to see what the Tower is like."

[Sure, Master! It sounds interesting, haha!]

"Good! Then, let's do a test to see if you qualify." Headon turned toward one of the murals and started walking while explaining, "In this Tower, every time you go up a floor, there is a test to see whether you are qualified to go to the next floor. If you pass the test, you can proceed to the next floor."

"Tests are decided by the Administrators and Rulers of each floor. Of course, the difficulty varies depending on which floor you are on…"

"In other words, if you want to go up to the next floor, you need to pass my test. And this is your test on the First Floor…"

As he finished speaking, Headon tapped one of the stone walls with his staff.

Following that, the wall seemed to melt down and was replaced with ornate iron bars. Behind those bars was a spacious cage-like room with a semi-transparent blueish water-like substance filling it and a humongous winged snake-like monster swimming inside.

"... The Ball," Headon finished.

Isaac's eyes narrowed as he saw the humongous eel-like monster in the distance, a monster that was as thick as a dram and several times longer than a slam.

The main problem was that Isaac hadn't yet experienced using his new powers and didn't know what level they would actually allow him to reach. That's why he was naturally slightly filled with apprehension.

[So that's the first enemy! What a big snake!... Look at the size of that thing!]

Isaac heard Mordred's voice that was more excited rather than scared, and it made him more relaxed. He woke up from his musings and turned to look back at Headon.

Headon slightly grinned and continued, "The Ball is a simple test. The Ball is that large black sphere. It is designed to pop when hit hard enough. To pass the test, the rules are simple. You need to go inside the bars and outrun or defeat that monster, then pop that ball, and you pass the test."

"The monster inside is a White Steel Eel. It is a big fish that lives in Shinsoo that flows through the Tower. Usually, it has a very mild temperament, but this time of the year happens to be its breeding season, and this one hasn't eaten anything for a few months, so it's very aggressive at the moment."

Headon loomed a bit closer and asked, "Do you think you could deal with it?"

Isaac slightly frowned. He roughly knew that his strength was around the level of his old Servant, but his instincts still inwardly told him that this monster wasn't a push over and posed a level of threat.

He was originally a magic user, not a physical fighter. The idea of suddenly rushing in and fighting in close quarters with a monster several times larger than Tyrannosaurus Rex naturally filled him with apprehension.

In a frontal confrontation, could he deal with it? What kind of strategy should he use?

As Isaac pondered, Headon added, "If you're afraid, you should go back home and you might still keep your life."

Isaac faintly smirked when he heard this. He was cautious, but it didn't mean he would back off.

He looked at Headon and said, "I'll take this test."