All the skills of the Bladedancer from the first levels to the third profession: what each one does, at which levels it is learned and which skills are worth learning.
Here we will list all the skills of the Bladedancer and give the necessary explanations that will help you in the game. The Bladedancers have some limitations in the class that do not let them spread out to the full breadth of their dark soul.
All the dances and some other skills require the Bladedancer to hold duals (paired swords). It does not matter what grade they are: if your Bladedancer is only for dances, you can run the whole game even with the worst D-grade duals.
All the dances of the Bladedancer have only the first level, so I will not mention it each time. The mana cost of the dances is progressive: if there is no dance on you, the first dance costs the minimum, the second spends more mana, the third even more, and so on.
And this mana limitation is tied not only to the dances but also to the songs of the Swordsinger: if there is no dance on you but there is some song, the mana cost will be the same as if you were already dancing the second dance. So you will not manage to sing and dance a heap of things on the party, because there will simply not be enough mana.
All the dances are cast on your whole party and last 2 minutes; so as not to sink too low in mana, the Bladedancer and the Swordsinger start buffing only when the last dance or song wears off, and try to launch their macros at the same time if the number of dances and songs is about equal. If the Bladedancer dances 5 dances and the Swordsinger sings only one song, the Swordsinger does it after the Bladedancer, so that the Bladedancer does not lose all the mana.
The professions: the first profession is Path to a Palus Knight, the second profession is described on the page of the class Bladedancer, the third profession is Saga of the Spectral Dancer.
The skills learned before the first profession
Weapon Mastery (passive): raises the character's attack. Three levels of the skill: the first is learned at level 5, the last at level 15, and it does not develop further.
Armor Mastery (passive): raises the character's defense. Five levels; like Weapon Mastery it is learned from level 5 to 15 and does not develop further.
Defense Aura (self-buff): a weak buff that raises physical defense. Two levels of the skill: learned at level 5, upgraded at level 20, and it does not develop further.
Mortal Blow (active): a chance of a lethal strike. A dagger in hand is required to use the skill. 9 levels of the skill: learned at level 5, level-ups until the second profession, and it does not develop further.
Power Shot (active): a powered shot from a bow. A bow in hand is required to use the skill. Overhit is possible. 9 levels of the skill: learned at level 5, level-ups until the second profession, and it does not develop further.
Power Strike (active): a powered blow in melee. A sword or a blunt in hand is required to use the skill. Overhit is possible. 9 levels of the skill: learned at level 5, level-ups until the second profession, and it does not develop further.
Attack Aura (self-buff): a weak buff that raises physical attack. Two levels of the skill: learned at level 10, upgraded at level 28, and it does not develop further.
Shadow Sense (passive): raises accuracy at night. When the skill switches on and off, a message is written to you in the system chat. Only one level of the skill, learned at level 15.
Drain Health (active): an HP drain. 53 levels of the skill: learned at level 15, the last level-up at level 74.
Heavy Armor Mastery (passive): raises physical defense when you wear heavy armor. Learned at level 20. It levels up every 4 levels until the second profession and does not develop further. 15 levels in all. Here the Bladedancers were really short-changed.
Magic Resistance (passive): raises magic defense. The skill is learned at level 20; it levels up every 4 levels until the second profession, every 3 levels until level 58, and every 2 levels until the third profession. 51 levels in all.
Shield Mastery (passive): raises shield defense when you hold a shield. And since you will be running with duals all the time, we have no use for it. Learned at level 20, leveled up at level 28. 2 levels in all.
Sword Blunt Mastery (passive): raises physical attack when using a sword or a blunt. Learned at level 20; 8 levels in all. It does not develop after the second profession.
Poison (active): hangs poison on one enemy. Learned at level 20; 5 levels of the skill in all, level-ups at levels 49, 58, 66 and 74.
Ultimate Defense (active): sharply raises physical and magic defense, as well as resistance to cancel and other buff-removing attacks. The character cannot move for the whole duration of the skill. Skill level 1, learned at level 20.
Deflect Arrow (self-buff): raises defense against arrows, cast only on yourself. Learned at level 24, leveled up at level 32.
Sting (active): deals damage to the target and causes bleeding. Overhit is possible, very often by the way; a sword, a dagger or duals are needed to use it. 49 levels of the skill in all, learned from level 24 to level 74.
Aggression (active): turns the target's aggression onto you. 12 levels of the skill in all, learned from level 24 to level 36, that is, only until the second profession.
Confusion (active): makes the enemy change the target of its attack. 19 levels of the skill in all, learned from level 24 to level 74.
Power Break (active): lowers the enemy's physical attack power. 17 levels of the skill in all, learned from level 32 to level 74.
Focus Mind (passive): raises mana regeneration. 6 levels of the skill in all: learned at level 36, level-ups at levels 43, 49, 55, 64 and 72.
Freezing Strike (active): lowers the enemy's run speed. 24 levels of the skill in all, learned from level 36 to level 74.
The second-profession skills
Dual Weapon Mastery (passive): raises attack power when using duals. Learned at level 40; 37 levels of the skill in all, the last learned at level 74.
Hex (active): lowers the enemy's physical defense. It makes sense to use it only when the enemy is very tough, a raid boss for example. Learned at level 40; 15 levels of the skill in all, the last learned at level 74. To learn the skill you need a book, which is knocked out of the mob Enchanted Monstereye.
Fire Dance (buff): increases the critical damage of all party members. Learned at level 40.
Dance of Light (buff): adds the holy attribute to the weapons of all party members in physical attacks, which adds damage to undead and demons. In Interlude it does not stack with the buff 
Holy Weapon, so it is either one or the other. One of the buffs works better on undead, the other on demons; which on which I no longer remember. Learned at level 43.
Dance of Inspiration (buff): increases the accuracy of all party members. Learned at level 46.
Dance of Mystic (buff): increases the magic attack power of all party members. Learned at level 49.
Dance of Concentration (buff): increases the casting speed of all party members. Learned at level 52.
Arrest (active): aggroes the opponent and roots it. Learned at level 55; 10 levels of the skill in all, the last learned at level 74.
Dance of Warrior (buff): increases the physical attack power of all party members. Learned at level 55.
Demonic Blade Dance (active): lowers the physical and magic attack of the enemies around you. Duals are required. Learned at level 55; 10 levels of the skill in all, the last learned at level 74.
Poison Blade Dance (active): poisons the enemies around you. Duals are required. Learned at level 55; 3 levels of the skill in all, the last learned at level 72.
Dance of Fury (buff): increases the physical attack speed of all party members. Learned at level 58.
Dance of Earth Guard (buff): raises resistance to earth attacks for all party members. Learned at level 62.
Dance of Protection (buff): raises resistance to falling damage for all party members. Learned at level 66.
Dance of Aqua Guard (buff): raises resistance to water attacks for all party members. Learned at level 70.
Dance of Vampire (buff): part of the physical damage is converted into HP; the vampiric percentage adds up with 
Vampiric Rage from a Shillien Elder or with 
Chant of Vampire from a Warcryer, which is what makes it valuable. Learned at level 74.
The third-profession skills
Health (passive): raises the character's resistance to the debuffs Poison and Bleed. One level, learned at level 76. To my mind it does not raise it much, because those same shamans in Ketra keep stubbornly hanging poison. But I learn it just in case. You never know.
Wisdom (passive): raises the character's resistance to the debuffs sleep and root and to mental attacks. One level, learned at level 76. A must for everybody: sleep and root do not matter much, because they will land anyway, but extra protection from mental attacks will not hurt.
Dance of Medusa (active): paralyses the surrounding enemies. Although it is called a dance, it is not a buff, so unlike the other dances it does not affect mana consumption. Learned at level 77.
Shadow Dance (buff): sharply lowers the run speed of the whole party and makes it invisible. It does hide you, but not from all mobs: the tyrannosaurs, the pterosaurs and the mobs in the rift will see you all the same. Learned at level 77.
Battle Force (active): used on a friendly character, it gives a +1 charge for casting the dome (the fusion skill). One level, learned at level 77. If you do not go to mass PvP fights, it is not necessary to learn.
Dance of Siren (buff): raises the magic critical chance of all party members. Learned at level 78.