Caster

"Both of you, sheathe your blades! You are in the presence of the king!" The newly-arrived servant – a red-haired giant of a man riding a bull-driven chariot – said in a booming booming. "I'm Iskandar, the King of Conquers! In this Holy Grail War I'm of the Rider class!" This introduction was followed by his master arguing that the whole point of this war was for one's identity to be kept a secret, but Rider didn't appear to be even listening to that boy. "Fate has brought us together to do battle for the Grail, but first I wish to make a proposition. What think you of yielding the Grail to me and joining my army? You would be treated as honored allies, and together we shall share in the joy of world conquest!"

"I'm afraid, I must decline." Lancer said, shaking his head at such a ridiculous proposition. "I may give the Grail to but one man: my new avowed lord. Not to you, Rider." Saber seemed to be in an agreement with him there. Furthermore, the blonde mistress of the sword seemed to have taken offense at the King of Conquerors for interfering with her battle.

"I'd be willing to discuss terms." Iskandar pressed, apparently hoping to for diplomatic solution here.

"That would be meaningless." A new, and surprisingly gentle, feminine voice spoke, prompting the three Servants on the ground to look for its owner. The said owner wasn't really hiding anyway: standing atop the stack of crates, there was a woman wearing long dark cloak with a hood covering her head completely. What was interesting, though, the bottoms of the cloak were on fire, but never actually burned away. "Letting such a precious relic be wasted on mere world domination? Everything will return to dust and everyone shall die under the terror spread by the beasts coming straight from your nightmares. Follow my lead, however, and the disaster might be averted."

"And who do think you are, mongrel, to believe that you have the right to lead the world?" The fifth Servant, a blonde man clad in ornate golden armor, said arrogantly as he materialized atop of a lamppost. "The world is mine, for I'm the one true king!"

"King you are or not, there exist things that you alone can't anticipate or avert. That is when the shepherds like me should take over and lead humanity away from the dangers." The cloaked woman replied in the same soft, almost gentle voice.

"Are you questioning my ability to rule my world, fool?" The golden Servant almost roared in anger. "You've sealed your doom!" He announced as a golden ripple appeared behind his back. A moment later, an ornate golden spear was fired from this ripple like an oversized bullet... Only for it to stop in the midair before it could reach its intended target. Then, as the still-cloaked woman lowered her extended hand, the spear fell harmlessly on the ground.

"This is most unfortunate." The mysterious woman continued, without raising her voice. "I just wanted us to be friends... But as you won't listen to what I have to say on your own, I will have have to use force to make you." With those words, she removed her cloak, letting the Servants and their Masters to finally see her face.

Probably not surprisingly, she was youthful woman, either in her later teens or in her early twenties. She had rather long dark hair, fair skin and strange, a bit inhuman, wineberry-red eyes. Her clothes consisted of sleeveless black jacket that clung tightly to her body, short black shorts with golden clasp on the belt, black boots that reached over her knees and black shoulder-long opera gloves. Somehow, though, those clothes didn't make her look like she was trying to seduce someone. Not that she would have any troubles with that if she tried – she was quite beautiful.

Raising her hand – and somehow summoning a ring of fire around herself along the way – the mysterious woman, the Caster of the Fourth Holy Grail War, snapped her fingers, creating an explosion right before the golden Archer's face out of the thin air. Unfortunately for her, it did nothing but irritate the once ruler of the world.

"You dare to raise your hand against your King, mongrel?!" Gilgamesh roared, a wall or golden ripples appearing behind him with numerous ornate weapons sticking out of them. Without any further warning, he fired those weapons at the Caster... But none managed to reach her as they encountered a wall made from strange dark-purple with colorful patches foggy matter that stopped those deadly projectiles dead in their tracks.

"King or not, your selfishness and arrogance are going to bring the world to its ruin." The black-haired young woman said, still using her soft and calm voice. "The same goes for you, the conqueror." She added, glancing at Iskander for a moment. "You shall regret not accepting my guidance today." Everyone expected her to pull some impressive attack, but there was none – she merely stared at Archer's ornate armor.

...Which quickly began heating up and within just a few seconds it was already red-hot, though not melting just yet. And despite its intricate design that seemed to take any possible dangers to the wearer into the account, it was getting noticeably uncomfortable for Gilgamesh to wear a piece of molten metal on his chest. So he simply banished it into his vault, revealing an expensive-looking caparisoned robe he wore underneath it.

"Mongrel!" He roared, summoning probably and entire hundred of portals with weapons. But before he could fire any of them, he himself got smothered by that strange foggy matter Caster had previously used to stop his attack. And, based on how the king of Uruk was jerking and flailing inside that fog, breathing was impossible for him. And seeing as this was just a spell but a matter manipulation, no matter how high Archer's Magic Resistance was, it couldn't do anything to protect him... Leaving Gilgamesh to die from suffocation, Caster turned her attention to the remaining Servants.

"And will any of you be my friends?" She asked almost innocently.

"I'm sorry, but just as I've said to the King of Conquers, I will give the Grail only to me new avowed lord." Lancer, Diarmuid ua Duibhe replied. In his head, though, he was also expressing his surprise at how his 'curse' seemed to have to effect on the Caster, even if she was both a woman and had little if any resistance to magics.

"Indeed, none of us will hand the Grail to you willingly. We all have our own reasons to desire it, and so we will fight to get it for our Masters and ourselves." Saber added, brandishing her invisible sword towards the dark-haired Caster. The said red-eyed woman let out a disappointed sigh, before summoning a wall of flames that trapped the other three Servants – and Rider's Master – in there with herself.

"That is most unfortunate..." She said softly. "It seems that you indeed have no desire to help me in my crusade to protect the world. So I shall make sure that you won't harm it with your misplaced actions instead." And as those words left her lips, a blade made entirely out flames burst from the index and middle fingers of her right hand held together.

Caster

True identity: Kili Surtr Muspelheim, the leader of the Dragon Cultists
Series: "Juuou Mujin no Fafnir"
Age: unknown
Sex: Female

Alignment: Chaotic Evil
Strength: D
Endurance: C
Agility: C
Mana: A+
Luck: E+
Persuasion: C → can influence the decisions of others through trickery or mind manipulation.
Independent Action: D
Item Construction: B* → is capable of temporarily manifesting most physical items into existence.
Territory Creation: E- → unable to construct even a workshop. Has no need for one, though.
Beastmaster: C+ → is capable of influencing dragons and equivalent mythical beasts.
Magic Resistance: C → is capable of blocking simpler magical and imaginary attacks.

Noble Phantasms:
D: A++, anti-unit (self). A human born with dragon's power. Kili has ability to convert dark matter into regular one at will. While there are few if any real limitations to this, she prefers to conjure fire and explosives. She can also do matter manipulation on already-existing items and – apparently a unique to her ability – can use dark matter directly. Furthermore, she possesses telekinesis and has an ability to rapidly move between distant locations by partially dematerializing herself.