Belladonna

This preparation based on the black berries of belladonna causes at first visual disorders (dilation of the pupils) then an acceleration of the heartbeat which can cause death on a delicate subject. The poison looks like a black liquid which however passes relatively unnoticed in food or wine.
A creature subjected to this poison must succeed on a DC 11 Constitution saving throw or take 2 (1d4) poison damage and its Dexterity score is temporarily reduced by 2. The creature must repeat the saving throw every 10 min for 1 hour to end the effect and recover its Dexterity score on a successful save, or take others 2 (1d4) poison damage on a failed one.