Grasp the Ghostly
Description: Requiring a full six hours of chanting, this ritual allows a necromancer to bring an object from the Underworld into the real world. It's not as simple as all that, however -- a wraith might well object to having his possessions stolen and fight back. Furthermore, the object taken must be replaced by a material item of roughly equal mass, otherwise the target of the ritual snaps back to its previous, ghostly existence.
Objects taken from the Underworld tend to fade away after about a year. Only items recently destroyed in the real world (called "relics" by wraiths) may be recaptured in this manner. Artifacts created by wraiths themselves were never meant to exist outside the Underworld, and vanish on contact with the living world.
Reference: Page 165 of the Revised Edition of the Vampire the Masquerade core book.