They are like formulas that, once etched onto the Soul, can be instinctively used without any practice, though their efficiency and effective use require varying amounts of practice and hard work, depending on talent and compatibility with the user.
An individual can gain Skills by five methods:
- By Birth or Evolution: A method that usually only applies to Monsters who are born with Intrinsic Skills based on their Race.
- By Acknowledgement of the Voice of the World: By achieving certain feats or by successfully using a Skill without having it yet, the Voice of the World grants the corresponding Skill directly to the individual in question.
- By Stealing from Others: Accessing the Soul of an enemy breaking the Spiritual and Astral bodies of target like Razen does, or using Skill-theft specific Skills like Gluttony or Usurper, allows one to acquire the target's skills.
- By voluntarily Granting duplicates of Skills: Through naming or via certain Skills like Gluttony of Beelzebuth, it's possible to share one's Skills with others.
- By Combining and Evolving Skills: By using certain Skills like Deviant that can fuse Skills, or by taking advantage of the Harvest Festival, it's possible to evolve Skills into stronger ones.
Obtaining new Skills has the downside that it lowers the Magicule capacity permanently each time a new Skill is acquired and that the capacity of Skills is based on the strength of the Soul.
Monsters can more easily gain Skills due to their high Magicule affinity, but in turn, Humans have more capacity for Souls due to a generally stronger Soul but have a hard time to obtain Skills in the first place, hence Humans usually focus on training their Arts instead.
Intrinsic Skill (固有スキル koyū sukiru, lit. "Inherent Skill") refers to the innate Skills that most Monsters possess. They are generally the same for the whole race, but Unique Monsters can be exceptions, and higher evolution stages likewise usually grant more Skills.
Common Skill (コモンスキル komonsukiru) refers to the most common of Skills.
Extra Skill (エクストラスキル ekusutorasukiru) refers to Skills with power and efficiency magnitudes higher than those of Common Skills.
Unique Skill (ユニークスキル yunīkusukiru) are fundamentally different from the lower Skills.
There are times when the mold of one's mind and its powerful wishes give shape to skills. This is the nature of what is referred to as a "Unique Skill." The process to acquire one is impossible without a mighty Soul, but among such beings, some can even have two or three of them.
A Unique Skill is the shape of the mind itself, meaning that those with a particularly weak ego have no chance to acquire one themselves.
In most cases, Unique Skills possess sub-Skills in addition to their main ability.
Ultimate Skill (アルティメットスキル arutimettosukiru), as it is called, is a device to grant access to the ultimate principles of the world. That is why, in order to combat against an Ultimate Skill, one must employ an Ultimate Skill as well.
Like with Unique Skills, Ultimate Skills also have sub-skills included.
Resistance (耐性 taisei) refers to a type of Skill that is generally passive and enables the user to withstand certain phenomena, both magical and physical. Among this type of Skill are "Resistances" and "Nullifiers," the latter being a considerably stronger version of the former.
Resistance-type Skills can be imbued into Multilayer Barriers and Magic Equipment to amplify the Resistance-type Skills' effects even further.