Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny maggot. The swarm can't regain hit points or gain temporary hit points.
Infestation. Melee Weapon Attack: +3 to hit, reach 0 ft., one target in the swarm's space. Hit:10 (4d4) piercing damage, or 5 (2d4) piercing damage if the swarm has half of its hit points or fewer. A creature damaged by the swarm must succeed on a DC 12 Constitution saving throw or contract a disease.
Each time the diseased creature finishes a long rest, roll a d6 to determine the disease's effect:
Base creatures are among the first to respond to sinister forces at work in a land. As nefarious powers grip an area, populations of maggots, scarabs, and similar scavenging insects explode and become aggressive predators. Roll on the Swarm Behavior table to see how such swarms might manifest.