Overshadow 2014
CR 4 undead
Large undead, chaotic evil
The overshadow can move through a space as narrow as 1 inch wide without squeezing.
While in dim light or darkness, the overshadow can take the Hide action as a bonus action.
While in sunlight, the overshadow has disadvantage on attack rolls, ability checks, and saving throws.
Actions
The overshadow makes two strength drain attacks.
Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 13 (2d8 + 4) necrotic damage, and the target's Strength score is reduced by 1d4. The target dies if this reduces its Strength to 0. Otherwise, the reduction lasts until the target finishes a short or long rest.
The overshadow dims the light around it. The radius of each light source within 60 feet of it is halved for 1 minute. The overshadow can't use this action while in sunlight.
Source: Tome of Beasts 2 (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details