Shroud of Sanguinius
It is kept in a box that is protected by a stasis field and is safeguarded by a Blood Angel known as the Guardian of the Shroud. Though if the stasis field is turned off by the Guardian, the Shroud will begin to give off psychic vibrations. While the Guardian himself is not affected by them, any nearby Blood Angels that are struck by the vibrations, will be driven into a frenzied state. However when the stasis field is reactivated, the afflicted Blood Angels will return to normal.