Shadow essence

[ Essence d'ombre ]
injury (mixture) - 800 gp
This black poison made exclusively by clerics from the essences of this undead creature is very powerful. One never fully recover.
A creature subjected to this poison must make a DC 14 Constitution saving throw. Its Strength score is reduced by 1d4 on a failed save, or by 1d2 on a successful one. The reduction lasts until removed by the greater restoration spell or other magic.
DnD 5e Poisons › Recueil des poisons d´AideDD