With an imperceptible flick of your wrist, you slip a newt's eye in your target's drink. By this time tomorrow, the king will be dead. You were never here. 

To cast this spell, your material component must touch the target’s skin. This can be through an attack or a sleight of hand check, such as a punch during a bar fight or an unnoticed nudge during a relaxed dinner party. One hour after the spell is cast, it begins dealing 1 poison damage each hour. The victim also acquires the poisoned condition at this time. These effects persist until a saving throw is made or the effect is dispelled by magic. While poisoned by this spell, a creature cannot regain hit points through resting. Hit points can still be restored by curative spells as normal. An affected creature may attempt a constitution saving throws at the end of any long rest, and the spell ends on their first successful saving throw. You may also apply this spell to a weapon that deals piercing or slashing damage. The next creature the weapon hits with an attack will be the target of the spell.

If cast at a higher level, the spell's hourly damage increases by one point for each spell level above second. 

Any spellcaster with second-level spell slots may learn this spell automatically if they spend an hour studying Zadoc's expertly-prepared instructional scroll.