(hey, Do. . . or I mean Spartanfan. It's me Ra. . . .heh heh heh)
Perhaps the amulet or rug would actually be a puzzle of sorts that must be solved to open the power to the owner. The rug would have a riddle, while the amulet would be like a rubic's cube the must be twisted in a specific order to be opened. Once opened the amulet maybe used by the one who solved the puzzle with his own hands.
What if there were consequences for turning the amulet in the wrong sequence? The effects could seemingly open the amulet for normal use, but, when used, it does the exact opposite of it's intentions. Another response could be that it vanishes and returns to the owner that possessed it last; maybe the creator of the item. This would put them back in the hunt and force them to research more about the item. Perhaps a certain sequence curses the character from ever being able to use the amulet again. Maybe all of the vampires that hold this item have all dialed this curse and are presently guarding the amulet from others.
Possible design: there could be a dial on the front with ancient Chaldean alphabet written on it, and two dials would be placed on either side with more letters; the letters would not be in order (like from a-z), but rather scrambled and repeated. Above the front dial would be a line where the letters are pushed into and taken out of to spell a word; only the side dials can transfer the letters into and out of the word line.
When the dials are turned in the right sequence"Shazam!" (or what ever.) the power would resonate within the character ready to be used. Then, once the power is used the amulet rescrambles and a new pattern or word must be solved to renew the magic.