(From: Reddit)
This is a perspective - written as if in character of a high-ranking and well-informed member.
About The Order of the Gauntlet
The Order of the Gauntlet is often considered a religious group. While many of the Order’s knights are of the faith, there is no requirement of this to join. All it takes is the zeal to fight unadulterated, pure evil. It helps to have a god or two looking over you though. Most of the Order’s work is preventative; cutting down cultists before they begin summoning rituals, or locking away a powerful artifact touched by a fiendish overlord. This tome is written to describe the harsher part of the job however, that of hunting fiends.
Fiends
Hunting Unknown is bitter work. It is a struggle that changes you, that haunts your very soul. There is little reward, and no end. Killing any fiend outside of their home plane is little more than prevention, as they will simply reform in the Abyss, Baator, or Gehenna. These beasts can hold grudges, killing one impermanently can be just as poor as not facing them at all, as they have eternity to devour you, your family, and anyone you ever came in contact with. Make no mistake, these creatures are not Orcs or Goblins, who might have some level of complexity in their morality, or some good among their flock. These monsters are just that. They are pure evil.
Devils
Next to the demons of the Abyss, the devils of Baator (or Hell, as many know it) are among the most well known fiends. In some ways, ironically, Devils are the simplest of fiends of the lower planes. Bound by strict laws following their overlord Asmodeus, Devils will make pacts with any who reach them. These contracts are always heavily in favor of the Devil, but if you are savvy enough, and the fiend is of the more foolish variety, you might be able to drag it back to your side to some degree. The Order does not condone making deals with Devils however as, beside the obvious immorality of the act, you can never truly get wool over the eyes of a Devil. No matter how smart you may think you are.
There is an angle with Devils that gives us the upper edge however. It is rare to find Devils working together completely. They scheme and connive against each other, like a macabre recreation of our own nobility. They might lead you to a rival Devil’s cult, or a powerful artifact their rival needs power from.
Never forget though, that they will stop at nothing to get their prize. Your soul. It is currency to them, and they treasure it above all else. Under no circumstances are you to allow them to claim it, lest you spend eternity in damnation as a maggot on the floor of Baator. If they have something you need, get it from them, but always kill them next.
Demons
There is a misconception on Demons. The idea that they are unintelligent brutes wreaking havoc upon the landscape, even in their native plane. While this is true for some, it merely scratches the surface of the monstrosity that is a demon. It is the act of fighting demons that keeps the Order at a small size. After all, it does not pay well, and the price of encountering a single Demon, let alone several, is high.
Demons corrupt. That is the universal truth on them. While the devil delights in striking a deal that purely benefits them, the demon lavishes in the moment that tarnishes a pure soul. A weak demon could poison the mind of a child, and convince them to kill her parents. A strong Demon, a Demon Lord, can influence thousands. Even the simple act of fighting demons is corruptive. Members of the Order rarely carry families. This is not because they are unable to, but because proximity with abyssal creatures has tainted their blood. Tieflings of abyssal origins are often created through taint such as this, and many members of the Order abstain from siring children to prevent their existence. It is a hard life to be a reminder of someone else’s pain, after all.
While there is technically a finite number of Devils in Baator, this does not hold true of Demons. Hailing from the infinite abyss, its native spawn is just as unyielding. This, combined with their raw power, makes demons a much more terrifying foe than any noble or lord will ever know.
All Demons are different, and as such require a different approach to fighting them. The best advice we can give in killing them though? Do it quickly, and at range if possible. Lest the taint set in quickly.
Daemons/Yogoloths
Lesser known than their fiendish associates, and in much less quantity, the Yugoloths (or Daemons as they are sometimes referred to) are a pariah amongst even the fiends of the lower planes. Acting as mercenaries and traders, the Yugoloth is loyal only to the deal. They are a beacon of neutrality within the confines of the lower planes. You might expect this to make them more tolerable, but it does not. If anything, a Yugoloth is much more a burden than any other fiend.
Yugoloths carry the worst features of both devils and demons. Like Devils, they delight in making deals and spinning lies, but are far superior in their ability to do so. And like Demons, the Yugoloths love to corrupt all that is good. Unlike Demons however, who do so on a base instinct and need to corrupt, Yugoloths do so on a moral obligation. They find the very virtue of “good” despicable, and will do all they can to crush it in entirety. While doing so however, they will convince you to give all your gold, treasures, and knowledge you have to them.
Yugoloths are famed in being master manipulators and deceivers, for this reason they view themselves above the other fiends as the “true” fiends of the lower planes. We speculate that they are behind the ongoing “blood war” between devils and demons.
As much as we hate to admit it, there is little many of us can do against a Yugoloth. Even the weakest among them require a team of seasoned individuals to bring down. The best we can advise is avoidance. The citizens won't like it, but it’s often better to let the Yugoloth finish its work, and deal with the consequences, than deal with the Yugoloth itself.