At a Glance
The fallen are skeletal undead, formed (rarely) when humans drown in magical mud.
Skeletons are the same height as living creatures (obviously) but roughly 1/7 of the weight. Human skeletons average 5 ft 9 in tall and 23 lbs (male) or 5 ft 4 in tall and 17 lbs (female).
Source
- Ruins of Undermountain [1060] adventure booklet, page 24