Hail of Stones was a card I was originally skeptical about. Once I realized that it effectively allows you to get rid of an enemy with the characters you would have used to attack it without letting it attack or contribute it's threat, It immediately found itself in quite a few decks of mine. Any effect that allows you to ignore enemy attacks is useful, especially with Hama or Book of Eldacar.
Hail of Stones
Action: Exhaust X characters to deal X damage to an enemy in the staging area.
Road to Rivendell #32. Tactics.
As mainly a solo player, this card was a true blessing while I was playing the Steward's Fear. You can use your cheap allies to chop some of those nasty bandits in the staging area before they get to engage you. I especially refer to the Zealous Traitors who can wipe your entire board in a single engagement. The Outland allies are perfect for that card since they are very cheap and also quite potent when they flood the board. One other thing, it's a very thematic card if you include it in a Merry, Pippin, Treebeard deck with a lot of ents. Eat these stones, Saruman!