Weariness of the Heart

The prowess of a character is modified by -1 until the end of the turn.
Alternatively, the target character is forced to make a corruption check.
Cannot be duplicated.

Shadowfax: "You might as well use a Corruption card instead." Yes, because they have capabilities OTHER than their corruption checks.

Turin: "There are a lot of better ways to go about the extra -1 to prowess...." Yes, or in most of them more than just -1.

Smaug: "This card would be much improved if it didn't go away so soon." Yes, since it's not Unique and there's none of that Non-Cumulative stuff, you could play a bunch of these and make Saruman a 1/9 wimp.

Morgoth: "One of the few that allows you to outright force a corruption check." You have a point, it does let you FORCE the check. Though I'd prefer a Lure card, which makes a Wizard do a -2 on any time at a Haven.

Tom Bombadil: "Great in a corruption deck, so-so in an attack deck (play this one on your opponent's Wizard to try for the win)." Yes, corruption checks do depend on this sort of card to win, and I do agree they're a good strategy.

Gollum: "Nice, but not that nice. Forcing a corruption check can be greatly to your advantage when playing this card." Same as above.

Cirdan: "Nice multi-use card, but neither effect is necessarily earth-shaking." Sums it up nicely.

Eru: "-1 to Prowess isn't that good." Once again, sums it up nicely.

Card names and spoilers are copyrighted by Iron Crown Enterprises, Inc., which reserves all rights in its intellectual properties.