The Soul Core is the internal structure that distinguishes an Awakened from an ordinary human. It is a metaphysical crystalline nucleus lodged in the soul, holding the bearer's essence (cosmic fuel).
Tiers
The Soul Core matures with rank: it grows richer, more complex, and acquires facets at every threshold (Sleeper, Awakened, Ascended, Transcendent, Supreme). At Supreme, the Soul Core becomes a miniature Domain.
Soul Sea
The metaphysical space surrounding the Soul Core is called the Soul Sea — an inner ocean where Memories, Shadows, and fragments float. Sunny sees his shadows walking and watching there in a strange light.
Combat Importance
Destroying an enemy's Soul Core is the only sure way to kill them permanently. The deadliest weapons (Slaying Blade) target the soul directly.