Swarm of Flies

You summon a vile swarm of bloodflies and send them to pursue a creature within range. The target must make a Dexterity saving throw. It takes 4d4 piercing damage on failed save, or half as much on a successful one.
If the creature succeeds the save and is still within range of the spell, it must repeat the saving throw at the start of your next turn as the flies continue to pursue it.
A creature that rolls a 1 on either save takes an additional 5d4 piercing damage.
At Higher Levels.
When you cast this spell using a spell slot of 2nd level or higher, both the initial and additional piercing damage increases by 1d4 for each slot level above 1st.