Tainted Sigil

(Requires Attunement)
This Sigil grants its wear +1 to attack rolls and to damage.
When put on it tightens so it can't be removed.
You experience dreams of torture, suffering, and
the demon within the Sigil. Black lines will
extend from the Sigil and cover the body. At
Dawn, the target must make a CON saving throw
or the darkness will spread. Once the darkness
spreads across the target, the curse is Permanent.