A great hit with champions of the undead and the not-quite-so-living. The hammers of Rot are an interesting weapon to wield and positively deadly to face. A hit from one of these weapons will transform the struck area into dead flesh or will strip it of its flesh depending on how injured the opponent is. The more damage an opponent takes the more he prematurely decomposes. These weapons are mainly found in the arsenals of undead champions, or are perhaps held by a necromancer who prefers to fight instead of wasting time and energy summoning the dead. It isn't that rarely that one can also be found in the possesion of a military commander or officer as well as with the undead.
As with every weapon of this sort however there is a downside, which in this case just happens to be that the more the wielder uses the weapon the more he gradually begins to look like a cadaver, and in time, perhaps over a period of years he becomes indistinguishable form a real cadaver.
Today very few of these weapons remain most having been found by paladins and other holy and righteous orders and destroyed. But they will come back to the surface every now and then, occasionally in the hands of the demented and oft insane. Go to Comment
With a huge number of sacrificial victims, another realm long ago secretly bound a Prince of the land spirits, Iorstonn by name, thus ensuring the fertility, and improving the magical defences, of their realm. But binding that Prince to one spot has disrupted the weather and magical patterns (ley lines?) over half the continent. Things have become bad enough that a coalition has been formed to rectify the situation, once divinations have established the cause.
Your party is one of the teams assembled to do the rectification: find the binding object and steal it ("so that we can destroy it here in our realm, of course"...*) or destroy it over there. Presumably the Prince will be grateful to his rescuers and angry at the binders, but with a greater spirit like Iorstonn one can never be sure: such beings are "tricksy".
* Of course, the rulers of our realm might want to control Iorstonn for their own ends...