Welcome, to a war waged in secret. A war of heroes and villains. A war of magi and the unfortunate mundane. A war waged in secret among seven participants, each summoning a great hero of the past to serve their will and fight their battles. But not all heroes are virtuous and when a wish is at stake, anything can and will happen.
This is a war over the Grail, a mystical object that selects seven 'masters' to control a hero of one of seven classes. Each master is marked by a unique rune on their dominant hand, and each master has a right to the grail as long as a 'servant' - one of the heroes - is under their control. Each rune also allows a trio of unbreakable orders to be issued to a servant - though after all three are used, the rune fades away - In fact, it's easily possible to trade control of servants to another - or steal it off their corpse.
Wizards don't always play nice after all. Past wars have featured serial killers, hired killers, treachery between masters, and the deaths of many participants. There are however, certain rules that are never violated, for they threaten the war itself.
The first is simple - once someone is no longer a master, they are no longer fair game.
Second - no revealing the war to the mundane world. To do so marks you for death among the magical community at large. Cover-ups aren't cheap or easy to do.
Third - All fighting must take place at night. This makes it easier to enforce the second rule and also forms a time that masters can rest and plot - or make alliances, or simply do whatever.
Fourth - Keep casualties to a minimum. This rule isn't exactly official, in all honesty none of them are 'official' to say, but came into being after one particularly determined master killed another one by bombing the hotel he was staying in. He killed his target but also brought the entire building down, killing hundreds of innocents.
Of course, there's the classes themselves; which are as follows:
Saber; Hero of the Sword
Archer: Hero of the Bow
Lancer: Hero of the Spear
Rider: Hero of the Mount
Caster: Hero of the Mystic Arts
Assassin: The Hero Killer
Berserker: The Maddened Warrior