A zombie is a fictional undead being created through the reanimation of a human corpse and as such they are most commonly found in horror and fantasy genre works. The term comes from Haitian folklore, where a zombie is a dead body reanimated through various methods, most commonly magic. Unlike Dungeons & Dragons, in modern depictions of the reanimation of the dead do not necessarily involve magic but often invoke science fictional methods such as carriers, radiation, mental diseases, vectors, pathogens, scientific accidents, etc.
Zombies look like what they are: animated corpses of a living creature. Imbued with the barest semblance of life, this shambling horrors obey the commands of its creator, heedless of its own wellbeing. Typical zombies are made of the corpse of a Medium or
Most zombies are created using a foul ritual. Once roused, a zombie obeys its creator and wants nothing more than to kill and consume the living. Corpses left in places corrupted by supernatural energy from the Shadowfell sometimes rise as zombies on their own, though. These zombies have no master and generally attack all living creatures they encounter.
Karrnath is a khorvairian nation which used zombies and skeletons as a military resource during the Last War. A karrnathi zombie resembles an ordinary human zombie wearing half-plate armor and carrying a light steel shield and masterwork longsword. However, it has been imbued with evil intelligence, and its desiccated flesh has been treated alchemically to make it more resilient. A dreadful stench typically heralds the arrival of one or more of these creatures. Karrnathi zombies are created from the remains of elite Karrnathi soldiers slain in battle. In the early years of the Last War, they were few in number and fought along side Karrnath’s living soldiers, but their numbers increased as the war progressed, to the point where the Karrnathi generals could mobilize entire divisions composed of Karrnathi zombies and Karrnathi skeletons.
Karrnathi zombies speak Common in a deep, scratchy, and guttural voice.
In your campaign
Zombies are mindless cannon fodder. Their strength is in numbers, so the best way to turn them into a really dangerous menace is to have them show in waves. One after another, a real zombie onslaught can be dangerous even for the most powerful heroes. And of course, you can always add special beasts zombies into the foray to make them specially lethal.
You can see the 5e’s stats for the zombie here.