Unholy Weapon
From AmtWiki
A Monster Ability. Text from By Night They Dance.
Description
Weapon is considered Red, magical, indestructible and anyone slain by such a weapon is considered instantly Severed. These weapons become normal in all regards while within the boundaries of Holy Ground and for a 100 count after being removed.
Currently, the Headless Horseman is the only known Monster to possess this "Ability." It is also unusual in that it is worded like a Trait, yet classed as an Ability.