Journeyman is my gaming system. It divides creatures into Animals, Aliens, Demons, Faeries, and the Undead. The Kleplok is a demon, and a relatively common one. My system is based on d10, so just double everything for d20.
Appearance: “Peering down the darkened stairs, you can just barely make out a mantis-like insect the size of a St. Bernard. Dull grey eyes stare myopically at you. As it turns, the jagged edges of its dead-white carapace scrapes gashes in the wooden walls of the stairwell.”
Victims: “The person has been horribly mutilated. There are long gashes across the body, probably made by the same instrument that left cuts and gashes in the walls and furniture around the body. The great number of cuts in the area suggests a madman of great persistence. The gashes are accompanied by deep punctures of various vital organs and sensitive places, suggesting that the victim was tortured before being finally dispatched. No gold is missing, but the clothing is destroyed and the armor badly damaged.”
Kleploks are extremely cruel and take pleasure in torturing their victims, whether they are supposed to or not.
Average HP: 69
Razor sharp Pincers  2d6 damage
Weakness: They take double damage from heat attacks.
Skills: Sneak , Sense , Climb 
Hostility: 95% chance.
Payment: 100 shillings worth of cane sugar apiece.
Service: Will serve at master’s side (like nasty guard dogs) or undertake one assassination attempt far away from master. A number of Kleploks can be summoned at the same time. The limit is placed at one Kleplok for every point of WILL that the magician has (thus, a mage with a WILL:8 can summon 8 Kleploks at once).