Sporous Crab

Amphibious. The sporous crab can breathe air and water.

Filthy. The sporous crab makes its home in grime and muck and is covered in filth. A creature that touches the sporous crab or hits it with a melee attack while within 5 feet of it must succeed on a DC 12 Constitution saving throw or be poisoned until the end of its next turn. If a creature fails the saving throw by 5 or more, it also contracts sewer plague. On a successful saving throw, the creature is immune to the crab's Filthy trait for the next 24 hours.

Multiattack. The sporous crab makes two claw attacks.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 4 (1d4 + 2) bludgeoning damage.

Spore (Recharge 6). The sporous crab sprays spores in a 15-foot cone. Each creature in the area must make a DC 12 Constitution saving throw. On a failure, a creature takes 7 (2d6) poison damage and becomes infected with the crab's spores. On a success, a creature takes half the damage and isn't infected with spores. After 1 hour, small bubbles and bumps appear across the skin of the infected creature. At the end of each long rest, the infected creature must make a DC 12 Constitution saving throw. On a success, the infected creature's body fights off the spores and no longer has to make the saving throw. If a creature fails the saving throw every day for 7 days, young sporous crabs hatch from the creature's skin, and the creature takes 9 (2d8) slashing damage. The spores can also be removed with a lesser restoration spell or similar magic.