One of the ways I tried to analagonize (that's not a word) how they work:
Have you ever been playing a new fighting game, but tried to input attacks from previous ones? And it works? You're a first-time player suddenly throwing out fireballs and canceling supers in an entirely brand-new situation. It's instinct, yeah, but you shouldn't have it by technicality.
Soulstones, in my headcanon, are just enhancements on those kinds of reflexes. Someone using one just gets the gut feeling of how to throw that one-two-kick combination, or how to brandish a spear to inflict painful, bleeding wounds, or how to manipulate aether to make their spells do specific things. Stuff you have no real training or experience in, but the powerful hunch in your stomach of what should come next.
Have you ever been playing a new fighting game, but tried to input attacks from previous ones? And it works? You're a first-time player suddenly throwing out fireballs and canceling supers in an entirely brand-new situation. It's instinct, yeah, but you shouldn't have it by technicality.
Soulstones, in my headcanon, are just enhancements on those kinds of reflexes. Someone using one just gets the gut feeling of how to throw that one-two-kick combination, or how to brandish a spear to inflict painful, bleeding wounds, or how to manipulate aether to make their spells do specific things. Stuff you have no real training or experience in, but the powerful hunch in your stomach of what should come next.