Taint

The caster evokes a word of malice and death, coating any object or spell in poison.

If used on an edible substance (such as water or medicine): When the substance is consumed by a living creature, it takes 2d6 poison damage and must make a save against being poisoned contested with the caster's spell save DC.

If used on a weapon: Any subsequent attack with this weapon for thirty seconds deals an extra 2d6 poison damage.

If used on another prepared spell: If the spell deals damage, add an extra 2d6 poison damage to the total damage. It cannot affect any other spells besides damage spells. Spells must take one action, reaction, or bonus action to cast.

For every level above 3rd: Add an extra 1d6 damage to the total damage of the spell.