Curse of Vile Parasites

While concentrating on this spell, your hands are imbued with a vile power that is capable of cursing creatures that you touch. When you cast this spell make a melee spell attack to a target within reach. On hit, the target is wracked with bodily pain and takes 5d6 necrotic damage, though Constructs are immune to this spell. While you concentrate on this spell, you can also use your action to repeat this attack, and targets hit are cursed with Vile Parasites. 

When a creature that is cursed with Vile Parasites dies, the corpse explodes into a Revolting Swarm made of undead fleshy insects, blood worms, or sliver-shaped crustaceans (your choice). If you can't see or hear the creature dying, the form of the swarm is chosen by the DM to suit the environment (crustaceans for underwater, insects for an aerial death, or worms if the creature dies on safe ground). The swarm resembles a revolting mass of the chosen form, which determines certain traits in its stat block. The creature disappears when it drops to 0 hit points.

The creature is an ally to you and your companions. In combat, the creature shares your initiative count, but it takes its turn immediately after yours. It obeys your mental commands (no action required by you) so long as you're on the same plane of existence. If you don't issue any, it takes the Dodge action and uses its move to avoid danger.

Swarms created by this spell are under your control for 24 hours, after which it stops obeying any command you have given it. Uncontrolled swarms will search for creatures to attack, spreading a wild or uncontrolled form of the curse on their own. To extend or resume control of the swarms for another 24 hours, you must cast this spell and succeed on a melee spell attack on them as above. A medium sized swarm can fit and be stored safely within a sealed bottle, satchel, or box.

At Higher Levels. If you cast this spell using a spell slot of 6th level or higher, for every slot above 5th the damage of the attacks increases by 1d6.