Looking at Rivendell Blade, a variety of restrictions stand out. The character must be Noldor or Silvan, the card is restricted, and the effect reduces defense, instead of directly boosting attack. However Rivendell Blade is still a very good card. You can attach it to any of those good Silvan attacking allies, while Elladan, Legolas, Haldir, and Mithlond Sea-Watcher are all good targets as well. The defense reduction is very nice and frankly, if the enemy has low enough defense to render the blade useless, it's probably puny enough to kill outright anyway. Very good card.
Attachment. Cost: 1.
Attach to a Noldor or Silvan character. Restricted.
When attached character attacks an enemy, that enemy gets -2 until the end of the phase.
Road to Rivendell #31. Tactics.