World:The Sixth Holy Grail War/Adapted FATE System/Servants
Servants are beings far different from normal humans, and as such they have different mechanical rules that govern their actions and characteristics as well.
Servants' skills and Noble Phantasms do not use the usual FATE ladder when describing their ability with said skill or Noble Phantasm; instead, they use the original system used in the Fate/Stay Night visual novel: a Servant's skill or Noble Phantasm can be of six different ranks, from lower to higher: E, D, C, B, A or EX. Each Rank can also be augmented, having its value doubled, tripled or ultimately quadruplet, if certain conditions are met, which vary from skill to skill, Noble Phantasm to Noble Phantasm - and not all skills or Noble Phantasms have this option, either.
EX ranks are especial, in that they do not fit into this category, because they simply cannot be quantified. They're generally impossibly powerful artefacts or abilities, the trump cards of the greatest heroes of legend, and nigh invincible in their fields. However, they also generally carry a cost to their usage, despite being all-powerful. Some examples of EX Noble Phantasms from the original material include Arturia's Avalon and Gilgamesh's Ea, the ultimate defence and the ultimate attack, respectively.
Servants do not share the same skills as usual humans; instead, they have access to a list of "heroic" skills. In game terms, the result of this is that Servants do not have ordinary Skills, and that these special skills are, in reality, a type of stunts. However, Servant Skills (or Stunts, in game terms) are graded with ranks, as per the Servant Ladder, and they usually have greater uses or effects than normal characters' stunts.
Servants have five attributes: Strength, Endurance, Agility, Luck, and Magical Energy. These attributes follow the usual Servant Ranks (E, D, C, B or A). When a Servant makes an attack roll (regardless if it is a ranged, magical or melee attack), he rolls his Strength Rank as a bonus. If the target tries to block the attack, then it is a contest between the two Servants' Strengths. If the target tries to evade, it is a contest between the attacker's Strength and the evader's Agility. The Endurance attribute sets the Servant's Stress track, on a rate of one rank to two Stress dots. Luck is the least used of Attributes, being only useful in specific circumstances (dictated by Heroic Skills or Noble Phantasms). Magical Energy is a special Attribute, in that by spending one Fate Point, the Servant can add his Magical Energy bonus to his other attributes for the duration of a scene, thus empowering him.
Noble Phantasms are the trump cards of Servants, and as such are treated in a special way in the mechanics as well - their Ranks follow the special ladder below, empowered in relation to normal Servant Skills. A C-Rank Noble Phantasm has the same attack power as an A-Class normal attack.
Relationship with Common Characters
Servants are Heroic Spirits that far surpass even the best of humans. The Servant ladders above refer to when a Servant clashes with another Servant, or when with a power suitably equal to theirs. When clashing with a normal human instead, Servants automatically get a +6 bonus on top of their own Ranks - even the lesser of heroes is at least Fantastic.
Limited Fate Points
Servants are incredibly powerful Heroic Spirits, but that means that they exist because of the tales and the belief in their stories generated by countless human minds. Their stories and legends set their actions and personalities, defining who they are and what they can do; this severely limits their free-will and their power of choice, and even their ability to change. Therefore, Servants are terribly limited in their use of Fate Points. For one, their Refresh Rates are permanently set to 1, meaning that they never refresh more than 1 Fate Point (though they can gain Fate Points by other means, and there are more ways to win Fate Points for Servants than there are for common characters - this is discussed below). Secondly, Servants CANNOT invoke aspects of a normal character or a scene that does not involve other Servants. Servants can only use their Fate Points when dealing with another Servant or a threat of similar power level to them. This levels the play-field between Servants and normal characters, giving the later a chance to at least escape.
This is explained within the game by the Holy Grail physically holding back the Servants to preserve balance in the world.
Mana and Fate Points
Mana, the energy that drives both magic and Servants, can be reasonably abstracted as Fate Points for Servants. Therefore, Servants can gain additional Fate Points whenever they have the chance to replenish their Mana: through their Master's constant supply (reflected in the Refresh Rate of 1), by eating the souls of people, by having sex, or by other, less known methods.