|Henry Justice Ford - Public Domain|
When found walking the earth or its dungeon depths they will have often already caused trouble for others and have remained in the area to enjoy the fruits of their labor.
Krimples are only found singularly, as working in pairs has led to Krimple-cide or worse.
Krimples stand 3' tall and when wrapped in a cloak and from a distance can attempt to pass themselves off as halfings. They smell of rotting flesh and any within 5' of a Krimple will notice such an odor, it is impossible to mask.
Killing a Krimple with non-magical weapons removes them from the prime material plane for 30 days. If they are killed with a magical weapon, they can not return for a year. Krimples find their time away from living creatures to be painfully boring, a year long exile even more so. They have been known to return after such a year with a mischievous vengeance.
Krimples can open and close locks, set traps, raise undead, sour milk, spoil wine, beer and the like, make food rot and other assorted nuisances at will. As a GM, be creative. They can also turn Invisible once per day, as per the spell. Duration is 1 Hr.
Swords & Wizardry Complete
Hit Dice: 3
Armor Class: 4 
Attacks: 1 Bite (1d4) 2 Claw (1d3)
Saving Throw: 14
Special: Assorted mischievous effects
Move: 12/12 (flying)
Challenge Level/XP: 5/240
Swords & Wizardry Light
AC: 4 HD: 3 Attacks: bite (1d6+2) Move: 12 (Fly 12)
Special: Assorted mischievous effects.