[center][h2]Demon Castle NAGATO[/h2][/center]
"...strong."

Murmuring these words, the resigned grin on the golem's face sharpened as he faced a horseman's charge. He paid little mind to the other Servants or the newly-risen fortress, even if two of his Partitions were monitoring them. If the Masters protected themselves, that was all the better. He didn't want to kill those who still had lives.

[i]...not strong enough, though. But that's good. One of the stronger ones falling first makes this all easier. If I wasted the reveal on killing a weaker one, it would be trickier.[/i]

Bright, bright, terrifyingly bright. As Rostam charged forwards, that tremendous multicolored light flared around NAGATO's right hand. The sheer presence of magical energy was absurd to the point of practically casting pressure.

But...where was this coming from? Not even the mana it had consumed upon arriving would be enough to match up. No, even if it had, didn't it need that energy to function? How could it continue moving if it was willing to move the entirety of that "fuel" to its hand?

[i]■■■■■ ■■■■■ System primed. Calculations complete.[/i]

Rostam was aware that what he faced would be a terrible consequence, but he was unaware of the magnitude it bore.

At this point, a question could be asked. In spite of its size, a Demon Castle was nonetheless a combatant "equal to a Servant". In that sense, it could defeat a single Servant, or perhaps two at once, or even more were it to target the Masters and force the Servants on the defensive at a result. But, against a group of this many Servants, a combatant equal to a Servant would lose without question. And yet, NAGATO had shown himself here, with full confidence that he could defeat the gathered spirits. 

Was he simply a fool? No, even if he bears the mind of Nagato Tohsaka, something with his calculative ability could not be so shortsighted. Rather, the reason he had come to this gathering with such confidence was simple. 

The Servants may have had their trump cards, but he possessed something beyond even those.

And this Servant who had dared to charge at him alone would witness it firsthand.

A radiance lit up the night as though it were day. Upon the golem's hand, a dazzling light collected to wage war upon those who stood against it. Not just Rostam, but every Servant, every Master, every living thing in the area could feel it. Something here was terribly wrong. Something here was an existence that was not meant to be in this world, and it was what lay responsible for that rainbow-colored light. An enemy of the world and an enemy of humanity.

...no. No, that wasn't it at all. Why would Nagato Tohsaka, a third-rate magus, ever be used for the core of a golem at the grade of a Demon Castle? It could not be for a mere rainbow.

That was the fatal misunderstanding born of this light. Not a rainbow. 

-A Kaleidoscope. 

[i]Jewel Sword System, [b]fire[/b].[/i]

Where had that magical energy come from? Why had the Demon Castle stopped its absorption of mana long before it reached its capacity? Why did it not fear the strike of Rostam or the charge of the beast he rode on?

The answer to all of these was the same. 

Multidimensional Refraction Phenomenon. Operation of Parallel Worlds. Kaleidoscope. 

The Second of the last remaining True Magics in this world. To its Magician was granted movement between worlds, access to their resources. To the sword of its Magician was granted a supply of magical energy as limitless as the number of worlds. 

And one of those very swords had just launched its counterattack.  

The light, that terrifying, kaleidoscopic light, ran forwards as Rostam attempted to pass by and strike at its wielder. A cone of light which released power on par with an A rank Noble Phantasm streamed out, moving to engulf Rostam and his steed before their charge met anything short of air. In a single burst of magical energy, a prime hero would be eradicated from this world.

In direct combat, NAGATO could likely outmatch Rostam, but against the team of Rostam and his steed, he would likely be defeated. However, that sort of theoretical loss would never come to pass, for just as Rostam possessed his steed, NAGATO possessed his sword.

This was the trump card of Demon Castle NAGATO. This was what made him worthy to challenge all the Servants of this war.