Junjo (5e Creature)
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Medium monstrosity, unaligned
Stench. Any creature that starts its turn within 10 feet of the junjo must succeed on a DC 13 Constitution saving throw or be poisoned until the start of its next turn. Creatures poisoned this way cannot willingly move closer to the junjo.
Multiattack. The junjo makes a bite attack. It can then use its Isopod Infection on the same target.
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) piercing damage.
Isopod Infection. The crustacean brain of the junjo attempts to crawl inside and infect another creature. One creature of the junjo's choice thats within 5 feet must succeed on a DC 13 Dexterity saving throw or become poisoned. While poisoned this way, creatures have disadvantage on Charisma checks and saving throws, gain the junjo's Stench feature, and attract other junjo. This effect can be ended if someone makes a successful DC 16 Wisdom (Medicine) check to remove the crustacean, if the target takes more than 20 poison damage in one round, or by use of the spell greater restoration.
Fish Head. The junjo drops its head, which retains its Stench feature. Until it completes a long rest, the junjo can't make bite attacks or use its Fish Head.
From the waist down, a junjo exhibits healthy, energetic humanoid anatomy. From the waist up, the junjo is a scaly-skinned fish that begins to decompose upon reaching maturity, its putrefying innards generating a steady stream of reeking, volatile gas. The true brain of a junjo is housed within a symbiotic isopod body, carrying with it the genetic information to replicate its complete outer body. Every six days, this crustacean retreats to the humanoid posterior while the rotting upper body is discarded completely, still floundering and belching gas while its brain-louse and posterior wander onwards, regenerating a new anterior in under thirty hours.
Variant: Dead Fish
Sometimes junjo can be created by necromantic magic, or rise from the dead through other means. These junjo have the undead type, are vulnerable to radiant damage, and replace half of any poison damage they deal with an equal amount of necrotic damage.