This spell is intended to be used by a mad mage my players are going to encounter, who's "spells" are all practical items that mimic the effects of magic. This will ironically be the only magic he knows, and the players will find a scroll of this spell in his lab.
Jar of Bees
Casting Time: 1 action
Range: 20 feet
Components: V, S, M (a sealed clay jar)
Duration: Concentration, 1 minute
You throw a jar full of angry bees, stinging and chasing the target. Make a spell attack against the target. On a hit, the target takes 1d10 slashing damage as the jar shatters against them, and they are surrounded by the swarm of bees. While surrounded by the bees, the target has disadvantage on concentration saving throws, attack rolls, and ability checks. At the start of their turn, the target must make a constitution saving throw or take 4d4 piercing damage, or half as much on a success. The bees can move up to 30 feet in a straight line on a turn: if the target moves more than 30 feet, the bees will choose a different creature within 10 feet. If their are no creatures close enough, the swarm disperses.
Classes: Bard, Druid, Ranger, Sorcerer, Warlock, Wizard
My comparison spells were Spirit Guardians and Fear; the damage is lower than spirit guardians, which is made up for by the extra effects and no saving throw. I intended for the damage to match a Swarm of Insects (Wasps). Fear has some similar effects, but no damage. I felt this spell still allows the creature to make attacks, and it is easier to end the effects of the spell (no saving throw to escape), which justified the added damage.
I like this spell because it could potentially make a chain of people trying to escape the spells effects, with the person concentrating deciding whether letting their ally take damage is worth the opportunity to pass the effect on to an enemy afterwards.