This article's content is accurate to the most recent public game version, 0.4.8d.
"Attacks all enemies with magical swords. Deals heavy Sharp damage."
Cost: 20 TP
Source: Eric(a) - Siphoning Eris' Core.
Blade Dance is a skill that deals high 
Sharp damage to all enemies. This skill also applies any status effects inherent to the user or their weapon.
Strong Sharp damage is hard to come by aside from a physical build Alice wielding a knife weapon, and physical attacks capable of hitting multiple enemies are even rarer. This skill is extremely useful against enemies more resistant to magic, or even just as a way to expend TP instead of MP for a powerful multi-target attack.
The following enemies can cast Blade Dance: