Medium undead. Chaotic evil.
Appears as a fainter version of a Shadow (see 5e MM)
Armour class 12 Speed 30’ HD 1D8 + 3 HP: 8
Str 4 (-3) Dex 12 (+1) Con 13 (+1) Int 6 (-2) Wis 10 (+0) Cha 8 (-1)
Skills: Stealth +4 (+6 in poor light)
Damage vulnerabilities: radiant
Damage resistance: acid, cold, fire, lightning, thunder, bludgeoning, piercing and slashing from nonmagical attacks.
Passive perception 10. Darkvision 60 ft.
Attacks:
Strength drain +3 to hit reach 5ft Hit 5 (1d6+1) damage, and target strength reduced by 1d4-1. If falls to 0, the target dies.
A subshadow will typically attempt to Hide , and then attack the rearmost character in the party after they have passed by.