Skills

Normal/No rank -

 * 'the ranking of most skills that can be trained by normal humans'

Hidden -

 * 'only a step higher than normal. However, they don't surface unless they are stimulated by other skills'

Special -

 * 'obtaining them mostly relies on talent & chance. Only 1 in a 1000 would have the chance to obtain one'

Unique Skills -

 * 'can only be obtained by 1 person, there can't be two people who hold the same skill.Only 1 in 10000 or even 100000 can obtain one'