Vulpen's Venom

A toxic bolt fires from your hands and flies toward a target within range and injects a poisonous venom into the target. Make a ranged spell attack against the target. On a hit, the target takes 3d8 poison damage immediately and must then make a Constitution saving throw, on a fail the target becomes Poisoned and lasts a number of turns equal to the spell's level. The target then takes d4 worth of damage equal to the spell's level, removing a d4 after each turn until the spell ends.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the initial damage increases by 1d6 and the spell's duration increases by 1 turn per spell slot.