Some of the inquisition reports are the sole information source there currently is concerning the feversleeps. From their brief glimpses of it, the inquisitors surmise a feversleep may be an adolescent form of a terrorsleep, or maybe the decrepit, old age stage at the end of a terrorsleep's days. The only thing that can be said with some certainty is that feversleeps are somehow related to the terrorsleeps, in whose company they are often seen.
Feversleeps emit a strange, sweaty heat. When victims draw near, feversleeps often cloak themselves in shadow, becoming invisible, detectable only by their foul stench and a strange weakening effect they have on their prey, distorting their prey's sense of time and draining its powers so they can feed on it.
Feversleeps love cool water, and are often seen next to pools or rivers, preferably underground in a dark and dank cavern. They have been seen mainly in Upper Roshamuul and are maybe attracted to ruins of ancients settlements, or may have had another purpose when the ruins were still inhabited. However, no one so far ever ventured to investigate closer, as the feversleeps are a promise of a slow, horrible end in the throes of deathly hallucinations, for all that stay too long in their vicinity.
Feversleeps have 5900 hitpoints. They are immune to earth damage and cannot be paralyzed. Moreover, they are strong against death, energy, fire, ice and physical damage. On the other hand, they are weak against holy damage. These creatures can neither be summoned nor convinced. In addition, they are able to sense invisible creatures.
Feversleeps yield 4400 experience points. They carry blue crystal shards, blue crystal splinters, bowls of terror sweat, cyan crystal fragments, gold coins, great mana potions, platinum coins, small amethysts, small emeralds, small rubies, small topazes, trapped bad dream monsters, ultimate health potions and sometimes other items with them.