Kastighur

"This hideous demon's body ripples with muscle. Its massive head is heavy with long horns while its powerful legs end in cloven hooves. Most of its head is hidden by an enormous steel helm that has been bolted to the creature's neck. A breastplate fastened onto its body provides additional protection for its already tough hide." ~ Monster Manual IV

Wicked and sadistic is the pure evil that is the Kastighurs. Acting as the Prison wardens and hunters they teleport around the field of battle and use their incapacitating charges to stun and horrify the enemies of the Tanar'ri.

Combat
Taking to battle with great joy and an immense love for melee combat, the kastigur will charge its enemies as often as it is able to and in combat it will attempt to stun adversaries and then rain its deadly blows on them. Combats starts with the kastigur charging its target, stopping at the limit of its swing (15 feet). If the target gets stunned another charge will commence, closing the gap between kastigur and victim. In close melee it will start making all-out attacks with its goring and slamming attacks dealing out catastrophic damage.

Teleportation
Three times per day a kastigur can use its spell-like ability to teleport at will. In battle it will often use a quickened teleport to appear 10 meters or more closer to a target so it may charge it. Battle fanatic as they are they might try to use their teleporting ability to appear above a flying target to then attempt to grapple it and take it down to the ground. As the kastigur takes to the field of battle it doesn't have time to become familiar with the battleground so it attempts to keep its teleports as close as possible. Kastigurs use their teleporting ability with a bit of trepidation because they don't enjoy the same greater teleportation that many other fiends have.

Planar travel
Since a Kastighur doesn't possess a reliable means of transporting itself from one plane to the next, it typically depends upon more powerful demons or even magical items to travel in this manner. A Kastighur also enjoys the pain and suffering that it can inflict on the material plane when it is called by a powerful evil spellcaster using a gate or greater planar ally.

Ecology
As many other fiends, kastigurs don't need to feed or drink - at least not in the same way as most mortal races. They feed off fear, panic and the hopelessness of those that they hunt or imprison. They take great joy in the hunt and torture of others, prolonging their deaths as long as possible, so they are able to savor the delicious emotions a little longer.

Appearance
Kastigurs stand somewhere between 15 and 20 feet tall and can weight around 10,000 pounds. They adorn their slowly glowing horns with carvings of symbols or words.

Society
Not terribly bright by nature, Kastighurs typically serve more intelligent and more powerful demons. They work as hunters and jailers among the Tanar'ri, roles in which they take great pleasure. When a Tanar'ri need to find a creature but lacks the power to create a retriever, it calls upon a Kastighur or two to hunt the individual down.

A Kastighur's appetite for fear and the hunt sometimes gets the better of it - a fact that can frustrate it's master. A Kastighur sometimes intentionally allows one of the prisoners to escape, just so it can hunt down the fleeing creature. On a battlefield, a unit of Kastighurs breaks rank to chase enemies who seem frightened. Left to its own devices, a Kastighur roams the abyss hunting and killing whatever suits its fancy, whether a damned soul or even another Kastighur. It sees others of its kind as competition for attention of the great generals and demon lords who can take it to hunting grounds on other planes.

Thus Kastighurs despise one another unless they serve the same master. Even then, they view their service as a competition, and each always attempts to outdo the other in feats of combat. A Kastighur that has managed to survive, and thrive, for a long time might grow to gargantuan size. Such a fiend looks for opportunities to enslave and torture creatures of greater power, including dragons, powerful mortals, and other potent outsiders.

Kastighur in Faerûn
Kastighurs make their home on the barrens of doom and despair, where they compete for service under Loviatar and Talona. They are frequently summoned to Toril to serve powerful spellcasters, such as Larloch, Manshoon, and Fzoul Chembryl.

Note
Monster Manual IV