Further Reading. While every effort was made to represent the gnolls in an original light, most of my inspiration comes from an article titled "Playing Gnolls." This supplement was written in 2008 by Keith Baker, most well known for the Eberron setting. Similar to his take on orcs, Keith Baker brings a level of nuance to a monstrous race that allows for unique motivations and rich cultures that go beyond simple bloodlust.
Though this article isn't readily available on the Wizards website (at least as I'm writing this), there are a number of ways to purchase the material elsewhere. The content there goes much further in depth than I could, and it is definitely worth checking out.
Gnoll
The gnolls are beastly humanoids--upright hyenas with an aggressive nature. Violence can send their body into fits of manic strength and speed. They prefer the company of their packs, and seldom engage with other creatures that they do not intend to eat.
Driven by Instinct
Of all the humanoids, gnolls usually have the most animalistic nature. They take simple pleasures, have painfully short lives, and rely heavily on their primal senses for survival. Their society is ordered into loose packs of associated families, with the strong or wise taking up positions of leadership. There's a deep bond between gnolls of similar bloodlines, and loyalty to one's kin is considered a virtue among all known packs.
Culture Shock
Gnolls have a number of customs that are shocking for more orderly races. Threats of violence are commonplace, as are vicious brawls between disagreeing members of a pack. Slights between gnolls are forgotten as quickly as they begin, often with lingering wounds exchanged.
This behavior is considered normal even among so-called friendly gnolls. For this reason, anyone that wants to do business with a gnoll must quickly learn to toughen up and take a few blows to their pride. Arrogant outsiders are beaten down, and may be slaughtered for meat if they insult the pack too much. Those that learn to play along with local tradition find much greater success than those who try to keep their hands clean.
Twisted Origin
The gnoll anatomy is a curious hybrid of magic and nature. Every bizarre characteristic can be traced to their infernal origin. The first gnolls came about when scavenging hyenas picked at the kills of Yeenoghu, a powerful demon that was loosed on the Prime Material Plane in ages past.
Though they can reproduce with live birth like the average mammal, new gnolls can be created by exposing normal hyenas to immense demonic magic.
It's unknown whether a gnoll could be created by different magic, but like Tieflings, this trace of demonic heritage runs through every living gnoll. Their hellish creation can be credited for a number of strange traits, such as an innate knowledge of the Abyssal language and a thrill for violence. While some Gnoll packs find other gods than Yeenoghu and seperate themselves from the Butcher's Brood, all gnolls speak Abyssal and gain surges of power when committing acts of violence.
Gnoll Names
Gnoll names usually consist of strung together Common phrases, usually words compounded to describe a gnoll's appearance, deeds, or personality. Baby gnolls follow similar rules, but quickly outgrow their birth names when they start to hunt and contribute to the pack.
Gnolls can gain new names throughout their lives. If an injury leaves you with an impressive scar, you may find yourself with a wholly new name based on this feature. This could go either way, as you're just as likely to gain a pathetic nickname like 'Fleaback' as you are to get a dignified title like 'Throatripper.'
Names: Bloodtooth, Festerflank, Blackgrin, Redeyes, Blackmane, Gutscar, Mangehide.
Gnoll Traits
Gnoll adventurers have the following traits in common.
Ability Score Increase. Your Strength score increases by 2, and your Dexterity score increases by 1.
Age. Gnolls live around 35 years on average, reaching adulthood within a few years of life.
Alignment. Wild by nature, gnolls are mostly chaotic and lean towards evil. Exceptions are few but do exist depending on pack.
Size. Gnolls are among the tallest humanoids, often standing between 7 and 8 feet at the shoulders. They usually weigh between 250 and 350 pounds.
Speed. Your base movement speed is 30 feet.
Darkvision. You are a nocturnal predator. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
Rampage. When you land a hit with a melee weapon attack, you can use a bonus action to move up to half your speed and make another attack with your bite. This movement does not provoke opportunity attacks.
Bite. Your crushing jaws can cause serious damage. They are a natural weapon that deals piercing damage equal to 1d4 + your Strength modifier.
Scavenger's Senses. You are proficient in the Survival skill. Whenever you make a Wisdom (Survival) check related to scent, you add double your proficiency bonus to the roll, instead of your normal proficiency bonus.
Predatory Kinship. Through sound and gestures, you may communicate simple ideas with all predatory beasts. They can understand your words, and you can understand them in kind. Additionally, you have advantage on Wisdom (Animal Handling) checks related to hyenas.
Languages. You can speak common and Abyssal.
Detect Balance Score: 24
Gnolls aren't significantly more powerful than the existing races found in the player handbook. They have a decent spread of flavorful gimmicks that should make them fun to roleplay, and offer unique moments to shine when your animalistic nature would be handy.
The biggest obstacle to playing a gnoll is lore-wise stigma against them. Depending on your setting and game world, gnolls may not be capable of higher thinking at all, and would make a bad choice for a party. As with most monstrous races, talk to your DM and figure things out ahead of time.
Also, it may be personal bias, but I tend to ignore obscenely short lifespans for player races. They've never made sense to me from a worldbuilding perspective, so feel free to give them around human-level life expectancy, if not a bit shorter.
Art Credits.
Illustration 1: Wizards of the Coast, Monster Manual