The Thorn Decree manifests as twisted black iron that slowly absorbs into its bearer's flesh over time - what was once worn becomes part of the wearer. The jagged thorns grow like gnarled branches toward the sky, occasionally blooming with dark metallic flowers that wilt when approaching the vault. It cannot be removed once claimed; it fuses to the soul itself, causing visible marks on the bearer's form that grow more pronounced with each successful incursion. The circlet pulses with dark energy when near the vault, responding to the bearer's proximity to the dragon's treasure.

The Thorn Decree serves as the vault's permanent marking - it represents the inevitable consequence of entering the dragon's domain, a transformation that cannot be undone regardless of whether one claims treasure or becomes another tale of failure in the dark. It is not a judge but a cosmic law: those who cross the threshold return changed, carrying the weight of the vault's attention forever.