I kept things as simple as they get.

First power levels:

F. E. D. C. B. A. S. SS. SSS

With ++and --

F++ means the very peak of the F-rank same for other ranks.

The rank is determined based on states for pets and beasts.

For humans, it's determined by a test, but generally speaking, as long as some can defeat a beast of a certain rank, that someone is judged to be of the same rank as the beast or higher. J

2nd attributes :

.... Strength:

[ related to physical power].

.... Agility:

[ related to nerve reflexes and speed].

..... Vitality:

[ related to resistance to both diseases and abnormal status, as well as defense and self-healing Factors].

..... Spiritually:

[ related to comprehension energy control energy capacity].

The extent of powers.

1 point equals the stats of a normal, healthy man. Either in strength, agility, vitality, or spirituality.

F rank is equal to 5 points, while F++ is equal to 10 points

E++ equals 100 points.

D++ equals 1000 points.

C++ equals 10,000 points.

B++ equals 100,000 points.

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A++ equals 1000,000 points

The stats of an S rank can no longer be calculated; relevant devices tend to malfunction immediately after use.

3rd Skills and abilities :

... Ability....

there are only 3 methods to acquire Abilities :

Inheritance is the process of a more powerful being sharing the same bloodline as you voluntarily passing an ability to you.

.. or through awakening the potential deep in your blood.

.. or by being born with it; in this case, it's called innate ability.

Ability grades: abilities are hard to judge and even harder to measure thus given no grading system.

Skills :

Skills are more common. They can be learned from others or skill scrolls.

Comprehended or even invented by oneself.

Skill grades: white. Green. Blue. Purple. Orange.

4th skill mastery :

..... Initiation:

You can only use the basic form of the ability without having any understanding of it.

... Primary mastery:

you can use everything the ability has to offer with some limits, and you have some understanding of it.

... Advanced mastery:

the ability is already part of your instinct, using it to its full potential, and you have a deep understanding of its workings.

... Perfected:

You already know all there is to know about the ability and can mold it however you want, going beyond its limits,

Perfected is related to one's understanding, comprehension, and a bit of luck.

Even if two people of the same race, same age, same gender, same talent, and power level, even with similar thinking processes, they can not have the same perfected skill or ability.

As for equipment and items let's make it simple from F to SSS.