Indestructible {T}: Add {B}. {6}{B}, {T}, Exile a creature you control: Harness The Soul Stone. ∞ — At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.
2025-09-19
"Harnessed" is a designation that the permanent has once an ability instructs you to harness it. It has no special rules meaning other than being a designation that the ∞ ability (and, theoretically, other effects) can see.
2025-09-19
Being harnessed isn't copiable. If something else becomes a copy of The Soul Stone, it must be harnessed separately. Similarly, if The Soul Stone is already harnessed and becomes a copy of something else, it stays harnessed, though it's very likely that won't be relevant until that copy effect ends.
2025-09-19
Until it is harnessed, The Soul Stone doesn't have the ability listed after the infinity symbol. It also doesn't have that ability in zones other than the battlefield.