For example Ruby
This knife originally belonged to [[Ruby]] and is capable of destroying most [[demon]]s if the stab wound is in an immediately fatal place, such as the neck or heart. Killing demons with the knife comes at the cost of killing their human hosts at the same time unless the vessels are already dead when they are possessed. When stabbed in less vital areas with the knife, the demon experiences intense agony but survives.<ref>[[4.10 Heaven and Hell]]</ref><ref name="six20">[[6.20 The Man Who Would Be King]]</ref> Its blade is inscribed with symbols and the handle is made from either wood or bone. Of all the demons that have been stabbed with the knife, only [[Knights of Hell]] such as [[Abaddon]]<ref name="eight12">[[8.12 As Time Goes By]]</ref> and [[Cain]]<ref name="nine11">[[9.11 First Born]]</ref> and [[Princes of Hell]] like [[Ramiel]]<ref name="twelve12">[[12.12 Stuck in the Middle (With You)]]</ref> have been shown to be immune to its killing power. [[Alastair]]<ref name="four09">[[4.09 I Know What You Did Last Summer]]</ref><ref name="four16">[[4.16 On the Head of a Pin]]</ref> was stabbed in the left shoulder both times, although both stabs were very close to his heart. [[Bobby]] is the only known person to survive being stabbed with the knife, having stabbed himself to kill the [[demon]] possessing him at the time,<ref name="five01">[[5.01 Sympathy for the Devil]]</ref> but the knife left him paralyzed from the waist down.<ref>[[5.02 Good God, Y'All]]</ref> It also has no effect on [[angels]],<ref name="four01">[[4.01 Lazarus Rising]]</ref> but it can kill [[hellhound]]s if the wounds are fatal.<ref name="eight14">[[8.14 Trial and Error]]</ref>
The knife is "an ancient demon-killing knife of the Kurds" described by [[Henry Winchester]].<ref name="eight12"/> How Ruby was able to come across it before she met Sam is unknown.
The knife has has been used to kill demons, humans, and hellhounds.
The white-eyed demon [[Alastair]] was never killed by the knife's demon killing power since both times he was stabbed were on the left shoulder.<ref name="four09" /><ref name="four16" /> However, [[Sam]] noted at one point that Lilith herself was scared of the knife,<ref name="four02">[[4.02 Are You There God? It's Me, Dean Winchester]]</ref> and she continually took precautions to avoid being stabbed with it whenever confronted with it.<ref name="three16">[[3.16 No Rest for the Wicked]]</ref><ref name="four18">[[4.18 The Monster at the End of This Book]]</ref>
[[Crowley]], too, has always avoided being stabbed with the knife.<ref name="five20">[[5.20 The Devil You Know]]</ref><ref name="six10">[[6.10 Caged Heat]]</ref> While Crowley stated that the knife couldn't kill him <ref name="ten22">[[10.22 The Prisoner]]</ref>, this may have been a bluff as he was later shown to be nervous in its presence when Dean pulled it on him after disabling him with an [[angel blade]].<ref name="eleven02">[[11.02 Form and Void]]</ref> Dean was later able to disable Crowley for a time by impaling the knife through his hand,<ref name="twelve23">[[12.23 All Along the Watchtower]]</ref> but Crowley eventually escaped somehow like he'd escaped a similar injury from an angel blade.<ref name="eleven02" /> After freeing himself, Crowley apparently retained the hand wound as he kept the hand that was stabbed wrapped up in a bandage.<ref name="twelve23" />