Spectral Leech

When you cast this spell, you kill the leech that is your material component with a pulse of necrotic energy, and place its ethereal form on the flesh of an enemy. Your target rolls a Constitution saving throw. On a failure, the target suffers 1d12 necrotic damage, and has disadvantage on all Constitution saving throws until the beginning of your next turn. For the spell’s duration, you can spend an action to inflict another 1d12 necrotic damage on the target and give it disadvantage on Constitution saving throws until the beginning of your next turn. On a successful saving throw, the target takes half of the initial damage, does not suffer disadvantage on Constitution saving throws, and you cannot spend an action in later rounds to cause further damage.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the initial damage increases by 1d12 for every slot level above 1st.