Incorporeal undead creatures with a touch attack that drains Constitution. Any humanoid slain by one becomes one in 1d4 rounds. Can sense and locate all living creatures within sixty feet as with blindsight. If they are caught in direct sunlight, they cannot attack and are staggered. Animals will not approach within thirty feet.
Larger, more powerful forms of these entities exist, known as Dread Wraiths. In addition to doing more damage and drain, they also have reach and possess the Combat Reflexes feat.
First Reference: Chapter 93
Other Notable References: Act IV Interlude Part 3, Act IV Interlude Part 4, Chapter 177