Bloater

Echolocation. The bloater can't use its blindsight while deafened.

Parasite. If the bloater reduces a humanoid to 0 hit points with any of its attacks, it becomes infected with fungal spores. It is unable to regain hit points unless an effect equivalent to the Greater Restoration spell is applied to it. At the end of the bloater's next turn, the creature transforms into an infected runner if the infection is not cured. Alternatively, if a creature is reduced to 0 hit points while under the effects of the bloater's poison (but not by the bite attack's damage), if it does not regain hit points after one minute, it is transformed into an infected runner.

Fungal Fortitude. If damage reduces the bloater to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is necrotic or from a critical hit. On a success, the bloater drops to 1 hit point instead.

Multiattack. The bloater makes two fist attacks. If the it uses its spores the bloater may make a fist attack as a bonus action.

Fist. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 17 (3d8 + 5) bludgeoning damage. On a successful hit, the target must make a DC 17 Strength Saving Throw or be grappled by the bloater. If a creature is grappled in this way, the bloater can make one additional fist attack against it as a bonus action.

Spores. The bloater tears a pustule of spores from its body and hurls it at a point within 40 ft, after which the spores explode in a 15 ft. radius sphere. The area is heavily obscured and lasts until the end of the bloater's next turn. When the spores explode, each creature within the area must make a DC 15 Constitution saving throw. On a failed save, a creature takes 10 (2d10) poison damage plus 10 (2d10) necrotic damage and is poisoned for 1 minute. On a successful save, a creature takes half damage and is not poisoned. A creature must make the saving throw when it enters the area for the first time on a turn or ends its turn there. The bloater and other variants of fungal creatures are immune to this effect.