As gleaned from a bout of drinking with the druid Erfetikk “Erf” Jedbo.
Out here in the Duchy of Ardeth and westward into the Kingdom of Utrecht the gnolls come hunting. The majority of them trek 600 or more miles off the Baedliks Plains under the eaves of the great Degerloch mountains though some have stayed to make life miserable all year round in the Lenfell and across the Larad Plains. Any why? For slaves, slaves to do their work for them, and as food.
Don't expect to find their older child bearing women folk or the young with them. No, the ones you run across are the veteran slave takers or the young males and females looking to make a name for themselves. All led by seasoned and experienced leaders who are adept at tracking, leading slaving parties far into human inhabited areas to raid and pillage, and capable of herding their people and captives home on the Baedliks Plains.
Though by nature Gnolls are disinclined to work or discipline: they will cooperate superbly on these hunts. They work in threes and when on the hunt will try to capture prey alive with their nets. If the prey is deemed too strong they will try to kill their quarry. Failing that they will retreat to alert the rest of the slavers of the threat and the leaders, after consulting with their priests, will decide on whether to pursue the matter or not.
Now gnolls worship demons, and worse. The various clans will follow anything they believe will give them an advantage. And sometimes those creatures will breed with gnolls. Most of these offspring become clerics or rarely a sorceror if they have draconic heritage and are the worst threat in the slaver groups. On the plains the different clans will and often fight with each other. But on the hunt even slaving parties from mutually hostile clans will work together.
It is said that some gnolls, destined for great and terrible deeds, will rip their way out of their mothers. One, known to use simply as "The Hand of Death," led a mass of clans and tried to take the Kingdom of Tegelen by storm a couple of generations ago. Gnoll leaders will use any name or title, and use the same names over and over again thus confusing things. The eastern Gadira Hills swarm with gnolls as they pass to and from their nomadic ranges in the Baedliks Plains. They make the Jentesi road pretty much impassable all by themselves. One of the main obstacles to the gnolls moving north of the Gadira Hills is the presence of copper dragons which feel it is good sport to hunt and kill gnolls in what they consider their territory.
Up into the Lenfell Forest and Gadira Hills are camps and areas used by the gnolls on their slaving raids for years. There they cull the weaker captives from those that appear they may be able to make the long trek, or at least part of the way before being eaten as the mass of captives are considered food first and foremost.
Gnolls dislike the day and prefer to operate at night though they know most humans and other prey are safely behind their walls. So they do and will move and attack during the day. Up in their camps most of the activity is between nightfall and morning. They eat nothing but meat and entertainment in a gnoll camp is to torment and torture a captive to death and then devour them. If hungry they will think nothing of cannabilism and treat one of the weaker gnolls in the same fashion. Never, ever expect mercy or compassion from a gnoll.
Unlike other hostile races gnolls do not work well with others. On a rare occasion either they will work with hobgoblins or bugbears but the arrangement does not last long. The only people who deal with or are tolerated by gnolls are members of the small tribes of demon worshipping humans found in valleys in the Degerloch Mountains. Ettins appear to think of gnolls as a delicacy for who knows what reason.
Gnolls usually consume their dead though once and a while a very evil and vile gnoll dies and the gnolls cannot stomach a body part of the dead gnoll. These they perceive as gifts from their fiendish dieties and the stronger leaders andpriests wear them. It is rumored they imbue various powers like detecting invisibility, seeing in the dark, and protections from fire or mundane weapons.
One thing that adventurers, mariners, and other people who have ventured into the Baedliks Plains has noticed: gnolls appear terrified of the sea and do not usually approach the coast unless coerced by a strong leader. The smell of rotten fish also repels them supposedly.
They speak their own language though some will learn Argossean, Hobgoblin, or other languages in order to assist with their slave taking. Their own language reaches pitches too high for humans to hear as do some of their horns which they use to signal each other.