Sword Skills
Sword skills are Echoes of Aincrad's special attacks. Each of the six weapon types has its own pool of around ten sword skills, unlocked as the player progresses through the campaign.
Equip Limit
Only two sword skills can be equipped on a given weapon at the same time. That limit forces a real choice between offence and utility, since a single slot can be the difference between a reliable gap-closer and a slow-but-devastating finisher.
How They Fit With Combos
Sword skills layer on top of the regular light and heavy attack combos rather than replacing them. They are strongest when used to extend a combo after a successful Parry Slash or Dodge Slash, where the enemy is briefly open to extra damage.