The soul sword is a piece of Illyana's soul that she turned into a weapon. It enhances the wielder's magical abilities and disrupts or destroys spells and magical entities, in addition to cutting through pretty much everything. It is the symbol of her potential as a sorceress because 1. she usually uses it instead of casting spells because her magical powers are too dangerous to use most of the time, and 2. because it is insane that a 13-year-old could create such a powerful artifact and weapon and that she even invented the spell involved.
The soul sword is a piece of Illyana's soul that she turned into a weapon. It enhances the wielder's magical abilities and disrupts or destroys spells and magical entities, in addition to cutting through pretty much everything. It is the symbol of her potential as a sorceress because 1. she usually uses it instead of casting spells because her magical powers are too dangerous to use most of the time, and 2. because it is insane that a 13-year-old could create such a powerful artifact and weapon and that she even invented the spell involved.