Secret skills are one of a kind martial skills. They have intelligence and choose their own master. Secret skills can be used by only one master at a time and cannot be shared, copied or taught to another. The true advantage of Secret skills is that they grow alongside their master. The more powerful their master, the more powerful the secret skill becomes though how far they can grow and how powerful they can become depends on the cultivation of their creator at the time of their creation. 
Secret skills choose their master mainly by the potential and talent above all else. Even though secret skills have intelligence and choose their own master, they can only choose from the individuals present before them. It does not matter if there is someone stronger other than the one selected is close by. Though if the secret skill does not find anyone it approves of, it will not choose a master and go into a dormant state until it senses someone worthy. Secret skills will only choose another master upon the death of their current master or if their current master relinquishes that secret skill.
Secret skills use a lot of energy but do not harm their user unlike taboo skills unless the secret skill is too powerful for the user, resulting in some backlash. However, Secret skills do put an enormous amount of pressure on the body. A regular martial cultivator may host one or two Secret skills. However, if they attempt to host three or more, their body would explode from the pressure. Hence, it is very rare to find a person who can truly host multiple Secret skills as well as a person who can fully comprehend and truly bring out the true power of a Secret Skill.
The powers of Secret skills vary with each secret skill. Certain Secret skills belong together as a set and can combine to be more versatile and grant unique and amazing abilities to their master. The Four Symbols Secret skills is an example of this. They can combine into a sealing technique or a slaughtering technique both with amazing power. So far, Chu Feng is the only master chosen overall to date who is able to do this.The forms secret skills take vary depending on both their creator and powers they have.Some after fusing with their chosen master lose their form and just grant their powers to their master while others take on simple forms like weapons but the most powerful seem to take on a avatar form which is the most versitale an powerful form they can take.As they can act seperately or in unison with their master to attack,defend,or support in some other way as they seem to retain their intelligence allowing them to act more independent.
Secret Skills have five levels, but Secret Skills are a little special and it's difficult to determine the level. Seven Realms Sacred Mansion has methods for Secret Skills, there are also some of the World Spiritists who master secret skill tiering methods. But everyone's assessment method is different, and sometimes the results are different. Therefore, the most authoritative judgment recognized by the world is that of the Seven Realms Sacred Mansion.
The five levels are:
|White Tiger Slaughtering Technique (4 Symbols)||Attack||?||Nine Provinces Continent||162||Chu Feng|
|Black Tortiose Armor Technique (4 Symbols)||Defence/Illusion||?||Nine Provinces Continent||301||Chu Feng|
|Azure Dragon Dashing Technique (4 Symbols)||Movement||?||Nine Provinces Continent||541||Chu Feng|
|Vermilion Bird Revival Technique (4 Symbols)||Healing/Recovery||?||Nine Provinces Continent||937||Chu Feng|
|Water Immortal Profound Technique (5 Elements)||Avatar||?||Holy Land of Martialism||1637||Chu Feng|
|Fire Immortal Profound Technique (5 Elements)||Avatar||?||Holy Land of Martialism||1677||Chu Feng|
|Wood Immortal Profound Technique (5 Elements)||Avatar||?||Holy Land of Martialism||2016 - 2017||Chu Feng|
|Metal Immortal Profound Technique (5 Elements)||Avatar||?||Holy Land of Martialism||2016 - 2017||Chu Feng|
|Earth Immortal Profound Technique (5 Elements)||Avatar||?||Holy Land of Martialism||2016 - 2017||Chu Feng|
|Ancient Era's War Sword (War Clan 9)||Weapon||?||Hundred Refining Ordinary Realm||2453||Chu Feng|
|Enemy Restraining Slash||Counter||?||Hundred Refining Ordinary Realm||2464||Chu Feng|
|Ancient Era's War Axe (War Clan 9)||Weapon||?||Hundred Refining Ordinary Realm||2469||Chu Feng|
|Six Demons Transformation||Avatar||?||Hundred Refining Ordinary Realm||2484||Chu Luxuan|
|Golden Winged Lion||Avatar||?||Hundred Refining Ordinary Realm||2531||Li Ming|
|King Among Swords||Weapon||?||Great Chiliocosm Upper Realm||2857||Han Yu
|Truesoul Division||Clone||?||Great Chiliocosm Upper Realm||3282||Chu Feng|
|Descent of the Demon Exalted||Avatar||?||Great Chiliocosm Upper Realm||3613||Chu Feng|
|Sealing Barrier||Restraining||?||Great Chiliocosm Upper Realm||3685||Gu Mingyuan|
|Jade Heavenly Beast||Avatar||?||Reincarnation Upper Realm||3780||Song Ge|
|The Divine Deer||Avatar/Movement||?||Reincarnation Upper Realm||3905||Chu Feng|
|Crown of the Phoenix Dance||Defend||Exalted||Darknight Sacred River||5122||Song Yuwei|