Shadow I enchantment (2nd attack)

The shadow I enchantment would apply to swords.

With the enchantment applied, when the sword is swung it would emit a 2nd attack 0.8 seconds later from the position it was swung. This 2nd attack would last as long as a normal attack and deal 40% of the damage of the sword that emitted it.

The attack would be a brief stationary sword projectile which would probably be faint, transparent, and vibrant dark blue.

The enchantment would be found on books within chests in the aincent city.