Khaless the Unforgettable has few worshippers among humans. Understandable, since before the Change he was considered to be fictional.
Fictional or not, the miracles performed by his followers are very real, and it's not just Klingons who are following his teachings now.
The fundamental tenant of Khaless's teachings is that life without honor is not worth living. Honor, in this sense, is very similar to the Japanese concept of face. Warriors should be ready to fight fiercely and die well. They should conduct themselves with dignity and be quick to disprove any insult or aspersion cast on their character or their fighting abilities. Comfort is a sign of moral weakness. Your word, once given, is binding beyond death.
Characters who chose to follow Khaless are expected to adhere to these principles; cowardly or dishonorable behavior usually results in healing being withheld until an atonement is made. Clerics of Khaless are all specialty priests, and gain the following abilities:
Clerics are allowed to take any NWP from the Warrior skill group without penalty. They may use any melee weapon they choose. They may wear any armor without penalty. They may turn undead.
All, Combat, Creation, Guards, Healing, War
Clerics gain +2 on their to-hit rolls when using the betleH.
1st level: Clerics may cast a form of strength spell that improves their Constitution. If the heightened score gives them a hit point bonus, the hit points only last for the duration of the spell, and any damage sustained comes off the temporary hit points first. They may cast this once per day, duration is 1 turn + 1 round/level.
3rd level: Clerics may cast haste (as the 3rd-level mage spell) on themselves once per day. The spell affects them normally each time it is cast.
The cleric may cast augury once per day.
7th level: The cleric may cast blade barrier once per day.
10th level: The cleric may cast speak with dead once per day.
When casting divination spells, the cleric is attempting to call on a spirit who has achieved Sto-Vo-Kor and seek their wisdom. At 15th level, the cleric is able to call on the spirit of Khaless himself via contact other plane. This may be attempted only once per month without risk. The risk is at the DM's option at to likelihood and severity of any negative consequence. At worst, the Fek'lhr may appear to haul the offending cleric to Gre'thor.
Clerics of Khaless may not use poison in any way in combat; this is a major transgression. They may, however, use narcotics, alcohol, and non-lethal drugs to capture or incapacitate. The question would be whether the use was specifically to take someone alive or if it was intended to kill them. Using a dose of narcotics to capture someone for interrogation purposes is not prohibited.
Clerics of Khaless are forbidden to disturb the dead; they may not animate undead or raise someone who has died. The dead have gone to their reward; their bodies are empty shells. To animate the body, though, is to risk the wrath of the person's spirit. Raising the dead is prohibited for much the same reason: the deceased has gone to his or her reward. Rescuing them from Gre'thor is unthinkable, and pulling them from Sto-Vo-Kor is just plain rude.
Although clerics have the ability to cure wounds and illness, they may often choose not to. Only the strong should survive. The best way to get healing from a priest of Khaless is to be valuable or useful in some way. Khaless considers it foolish to lose a valuable resource when you have the power to keep it. Expect to be mocked, though.
Clerics of Khaless are expected to be the first to enter battle, and the last to leave. They should seek out glorious battles and die with a song on their lips. They should live according to the ancient adage,
"Heghlu'DI' mobbe'lu'chugh QaQqu' Hegh wanI'"
"Death is an experience best shared."