Nightcat of Soulscorch
These nightmare cats roam the Soulscorch desert.
The are immune to heat and need no water or typical substance to survive. They hunt only to steal the souls of both animals and humanoids. While they are efficient hunters, the soul is not so easily captured. Every time the cats bite a victim and the attack roll is a natural 20, they steal a level from the victim. If the victim is somehow helpless the cat can wait a round to attack. For each round the cat waits the number needed to roll drops by one.
The cats can run at full speed for several hours, roaming their vast desert home. When food is scarce, they make raids into more inhabited areas.
They are not undead and can't be turned. They are about 4 feet high and are strong enough for small humans and humanoids to ride.