The three shield staves:

Item Name Mob Elemental Shield
a jade cameo Captain Lodd ice
a sorcerer's walking stick Captain Faragut shock
the Staff of Barad-dur Sauron fire

Each stave will cast its elemental shield on every player in the room.
This is very handy for runs, especially if you have a lot of people.
Because they are used so frequently, they are often sold in bulk.