Legendary heroes of the past are summoned to the modern world and once again given flesh to participate in an epic war to get the Holy Grail. An omnipotent artifact capable of granting any wishes whether it be for a pure or corrupted cause.
Fate/Prototype is based on an unfinished novel that Kinoko Nasu wrote during highschool. It was the basis for the visual novel Fate/Stay Night before they changed the script to reflect on their target audience.While most of the characters are changed in some way, some Servants didn't. They are Berserker, Caster and Assassin. This is probably why they weren't shown in the preview.
The Saber-class Servant excels in close-ranged combat and is considered the strongest Servant in every war. This hero is known as the legendary king of Britain and wields the strongest holy sword of all, the Excalibur. This sword was so powerful that each Knight of the Round Table placed a seal on it to prevent the sword from being abused.
The 7th Master participating in the war and also Saber's Master. She lost her father and older sister 8 years ago to the previous Holy Grail War. Because of that she wishes to escape her fate and doesn't want to participate in the coming war, but because she have accidentally summoned Saber during the chaos with Lancer, she must now finish what she started. Her command spells are located on her chest.
She practices black magic instead of the more modern form of sorcery which is magecraft. She also have a major inferiority complex because of her older sister who was a great genius when it comes to magecraft.
The Archer-class Servant excels in long-ranged combat and is capable of firing projectiles to attack the enemy. This legendary hero is known as the oldest king ever recorded and the only known hero to have acquired all the treasures in the world. He wields the the golden bow, Enki, which is capable of summoning a great flood that could submerge a whole city in an instant.
The 3rd Master participating in the war and also Archer's Master. Nothing much is known about this person, not even his name. His command spells are obviously located on his face.
The Lancer-class Servant excels in speed and the use of spears which allows him to combat foes in mid-range. This legendary hero is known as the child of light and wields the cursed spear, Gae Bolg. His Master sealed the cursed spear and prevented him from using it, so he uses a wooden spear instead which later broke after an attack from Saber's invisible sword.
The 2nd Master participating in the war and Lancer's Master. She wants to summon a hero who died because of a woman, that way he'll know how scary women really are. Her command spells are located on the back of her neck.
The Rider-class Servant excels in mounted combat. They can ride any vehicle or large animals and is also capable of summoning their own form of transportation. This legendary hero is known for killing the snake monster Medusa. He wields five different artifacts and rides the winged-horse Pegasus. Since his Master died before the war ended, he swore to win the war and get the Holy Grail to revive his master and give him the life he rightfully deserves.
The 5th Master participating in the war and Rider's Master. He didn't last long in the war because of his health condition but used up all his command spells just before dying to give Rider a second chance at life. His command spells are located on his left palm.
The unnumbered Master participating in the war and Berserker's Master. He is a two-faced priest, one moment he's calm and understanding and then all of a sudden he goes batshit insane and starts shouting all over the place! This guy is crazy, I tell you! His command spells are located on his tongue.
She is Ayaka's older sister who supposedly died in the war 8 years ago. She is once again given life by the Holy Grail to participate in the war all over again. She used to be Saber's Master during the previous war but he betrayed her after he discovered that this girl is actually a psychopath who killed her own father and tried to kill her younger sister. Now that she's back, she wishes to once again be reunited with her prince charming, Saber. Her Servant is the embodiment of humanity's sin, the Beast. Her command spells are also located at her chest.
I must say that the character designs are a lot better than FSN, especially since Cuu Chulain is no longer wearing blue tights and looks more like a hunter now. Saber is now actually a male too, which is more accurate to King Arthur's historical record. Oh well, just watch the short clip below to understand what I'm blabbering about:
This video was uploaded by someone else and will probably be taken down after a while because of copyright issues. So I highly suggest that you watch it now before it goes down.