Cheat sheet for ranks of statistics.
TLDR: F is an average human, E- is early Advanced rank, E is Advanced rank, E* is peak Advanced rank, D is Saint, C is King, B is Emperor and A is God rank. More info below.
F- = weak human/child
F = average human (-100 kg strength)
F* = early Intermediate rank (trained human~peak athlete; 150-500 kg strength; Rudeus)
F+ = true Intermediate rank (surpassing human limits; 250-1000 kg strength; most characters in the series; Elinalise, Sara, Sylphy (matches reaction speed of people in Sword Sanctum), Luke (probably), Roxy (has high physical strength that surprised Rudeus))
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E- = early Advanced rank(x2 human genetic limit; 1,000 kg strength; 12-year-old Eris)
E = Advanced rank(early Paul/Julius)
E* = peak Advanced rank(peak Paul)
D- = early Saint rank
D = Saint rank(x8 human limit speed; Rudeus in Magic Armor)
D* = peak Saint rank
C- = early King rank(North King Wii Ta (halfling))
C = King rank
C* = peak King rank(Ghislaine)
B- = early Emperor rank(current Hector (OC))
B = Emperor rank(peak Hector, Auber Corvette, Sword Sanctum's Sword Emperors)
B* = peak Emperor rank(Ruijerd)
A- = early God rank(Randolph Marianne, Ogre God (probably))
A = God rank(Sword God, Water God, Kalman III)
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1.2 A = high God(Jino Britts)
1.4 A = peak God(First Sword God, First Water God)
1.6 A = Beyond God(Fighting God, Technique God (probably))
1.8 A = Beyond God(Orsted, Laplace)
2x A or A+ = True Divinity(Orsted, Hitogami)
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The ranks mirror parameters in Fate. It's mainly for physical stats, but Mana is similar. In Mushoku Rank doesn't equal strength, but it also does to a degree…
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Statistics explained:
Strength - physical strength
Endurance - body's durability and resilience; also stamina
Agility - speed and reaction speed; also agility
Mana - Mana Capacity and Mana output
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Note: Normally Battle Aura/Mana Reinforcement gives a uniform boost to all statistics by default, but depending on the MC's age and his body, it would be represented differently in his statistics. For example, as a child Mordred would have thin muscles and short legs, so his effective Strength and Agility would be low, but his Stamina (resilience) would be way higher. His relative 'running speed' would also be low, but his reflexes and the speed of his sword would be a few times better, which will be shown in a bracket.
A 'plus' modifier originally means that the value can be doubled momentarily or in certain conditions. A++ means that it can be doubled by a factor of two, for a result of 3x A, or simply means it can be multiplied by 'a lot'. The reason I don't simply use something like 'D+' for peak Saint rank is because of this.
A 'minus' modifier in abilities is used in cases where an ability doesn't quite reach the assigned rank, has some drawbacks or only reaches it in certain conditions.
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PS: As you can see, the story has Fate in the title, but early on there is no Fate content or Fate characters; rather than a crossover it's just a Mushoku story with the Main Character having some minor Fate abilities and Mordred in name. This might change eventually, but not quite before the entire main story concludes.