The corrupted waters of the Marshes of Madness act as a repository for the taint of Chaos that engulfs the land. As the greenish vapors distort the mind, the water acts upon the bodies of all those foolish enough to drink of it. The outcomes of a single draught are many and varied. A very fortunate few escape unharmed, while others soon develop an infectious fever that ravages the body. The only early warning sign of the sickness is excessive perspiration, a common enough side-effect of the sultry marshes themselves. It is only in the final hours that the ague is revealed as the deadly monster it is, as victims suffer massive internal bleeding ... and infect anyone who attempts to offer them aid.
Approach a Rotting Ratman between a tree and the edge of a swamp pool at 15400,30900 in the Marshes of Madness. You don't need to click the corpse, simply walk on or near it.
This tome unlock contributes to the Dangers of Deadwater exploration achievement.
Reward: 150 Xp