Midnight tears

ingested (mixture) - 1500 gp
MixtureA creature that ingests this poison suffers no effect until the stroke of midnight. If the poison has not been neutralized before then, the creature must succeed on a DC 17 Constitution saving throw, taking 31 (9d6) poison damage on a failed save, or half as much damage on a successful one.
Dungeon Master´s Guide
  1. DnD 5e Poisons › Midnight tears