Crotch Goblin

Shapechanger. The crotch Goblin can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a wasp (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Devil's Sight. Magical darkness doesn't impede the Crotch Goblin's darkvision.

Magic Resistance. The Crotch Goblin has advantage on saving throws against spells and other magical effects.

Sting (Bite in Beast Form). Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) piercing damage, and the target must make a DC 11 Constitution saving throw, taking 10 (3d6) poison damage on a failed save, or half as much damage on a successful one.

In addition a second DC 11 Con saving throw must be made or become infected with Shivering Sickness. A creature with natural armor has advantage on the saving throw. It takes 2d6 hours for symptoms to manifest in an infected creature. Symptoms include blurred vision, disorientation, and a sudden drop in body temperature that causes uncontrollable shivering and chattering of the teeth.

Once symptoms begin, the infected creature regains only half the normal number of hit points from spending Hit Dice and no hit points from a long rest. The infected creature also has disadvantage on ability checks and attack rolls. At the end of a long rest, an infected creature repeats the saving throw, shaking off the disease on a successful save.

Invisibility. The crotch goblin magically turns invisible until it attacks or until its concentration ends (as if concentrating on a spell). Any equipment the imp wears or carries is invisible with it.