Guarded (enemy or location).
While Banner of the Serpent is attached to an encounter card, each Harad enemy gets +1 
Action: Exhaust Banner of the Serpent and raise your threat by 1 to give each Harad enemy engaged with you -1 until the end of the phase.
Attach to a hero.
Attached hero gets +2 
and collects an additional resource during the resource phase.
...the necklace of Girion, Lord of Dale, made of five hundred emeralds green as grass, which he gave for the arming of his eldest son...–The Hobbit
Attach to a hero.
Each unique character you control gains +1 .
Action: Reduce your threat by 2 to attach The Arkenstone to a hero controlled by another player and raise that player's threat by 2. (Limit once per round.)
Attach to a hero or Gandalf. Restricted.
Attached character gets +2 .
Attach to a hero. Restricted.
Attached hero gets +2 .
Response: After attach hero destroys an enemy, add 1 resource to attached hero's pool.
Guarded (enemy or location).
Attach to a Dwarf hero.
Action: Exhaust Ring of Thrรณr and discard the top card of your deck to ready attached hero. If the discarded card is an attachment, put it into play.