Oh a Duergar, wasn't aware they had advantage on saving throws.
In that case you could also eat any rotten food; it gets you poisoned by default and gives you disadvantage on all checks. Rotten food is how I intentionally fail a certain persuasion dialogue check in Grymforge, so I can legitimately provoke the Duergar slavers to attack me.
Wouldn' drinking a bottle of wine or liquor help also ? In drunk state you have disadvantage I think. It seems a more pleasant way to cripple a roll than eating rotten food.
