A Death Knight stands at 2 meters tall with a crooked body. It is equipped with a rippled sword called a Flamberge and a huge shield known as a Tower Shield. Death Knights are looked upon as huge creatures equipped with armor made of black metal with red bloodlines engraved on it.
Moreover, the armor has sharp thorns everywhere and looks like an incarnation of violence. Two demonic horns protrude from the helmet, with the face being visible underneath. It has a disgusting, rotted face whose empty eye sockets are filled with hate and killing intent, glowing with a flashing red light.
In the anime, its left-hand holds a massive Tower Shield that covers three-fourths of its body. Whereas in its right hand is a serrated sword. The sword is nearly one hundred and thirty centimeters long and coated with waves of terrifying red and black fog, agitating observers from nearby like a constant heartbeat.
Death Knights, even though they have massive bodies, are extremely fast and are capable of gaining enough momentum to use their bodies, along with their tower shield, to act as a living battering ram. Their physical strength along with their weapon can cleave any unfortunate soul that gets into their way in half.
Death Knights have two very important special skills. The first is the skill of drawing in the hate/aggression of those disturbed by the Death Knight's appearance to attack it. The second one can only be used once upon getting hit, but it allows the Death Knight to always survive one lethal attack as long as there is a certain amount of HP left. In other words, a Death Knight can survive anything fatal with 1 HP remaining no matter what kinds of attacks are thrown at it no more than one time.
Because of these two special skills, a Death Knight is often used as a meat shield by their summoner to protect themselves from any harm. Nevertheless, Death Knights are closely estimated to be level 35 monsters, due to having both the attack power of a level 25 and the defense power of a level 40. Ainz estimates that someone who can defeat the defense-oriented Death Knights by themselves will probably be over level 45.
Additionally, once a Death Knight manages to kill its intended target, that dead body will later end up turning into an undead. For those killed by a Death Knight, it is said their body reanimates as a level 17 Squire Zombie, the kind estimated to be half a Death Knight's level. However, the number of Squire Zombies that can be made at any given time has a limit. What can be particularly frightening about the Death Knight's skill of turning the people it kills into Squire Zombies is that those same Squire Zombies can also make zombies too from the targets they kill. There is no limitation on how many regular zombies can be created by Squire Zombies. However, the zombies will revert to regular corpses if a Death Knight is to be destroyed first.
In the New World, there is a naturally-spawned Death Knight that kills its foes and turns them into undead ghouls.
- According to the author Maruyama, native Death Knights in the New World are transcendentally rare. He said they naturally-spawn every 100 years or so.
- Based on the Web Novel, Maruyama said that if a native Death Knight in the New World is to continue existing for a long period of time, it may someday evolve to be called a Lord.
- According to the game’s rules in YGGDRASIL, the souls who fell to the Death Knight’s blade would become its slaves for all eternity.
- In the Web Novel, the Death Knight almost won the duel that would have killed Gazef Stronoff if Ainz Ooal Gown did not step in. It also fights the Martial Lord in the Grand Arena.
- If a Death Knight is summoned normally, it will cease to exist after a short time, but if it is summoned in combination with a corpse, the Death Knight seems to become a permanent existence.
- In the Web Novel, by YGGDRASIL standard, the summoned Death Knight should disappear after 100 minutes have gone by.
- One Death Knight was captured by the Baharuth Empire five years prior to the appearance of Nazarick.
- One of Ainz Ooal Gown's Death Knights is currently training to see if it can gain levels and learn martial arts. While it is still unknown whether or not the Death Knight can learn martial arts, Ainz notes, however, that leveling up seems impossible for this undead.
- Originally in YGGDRASIL, the Death Knight should have stayed by its summoner’s side to await their orders and attack any enemies that approached. Yet due to the difference in the New World unlike in the game, it can actually leave its summoner to fulfill its orders, launching an attack of its own accord independently.
- A guild's mercenary system that summoned creatures in exchange for YGGDRASIL currency did not allow for the summoning of Death Knights.
- In the anime, a Death Knight is shown to teleport to its victims but was only shown that one time.
- In the Web Novel, Maruyama describes how Death Knights smells unexpectedly smelly, "the scent of a graveyard wafts off them, as well as the earth." But the mantle appears to have little smell. When Ainz used them during the Imperial Magic Academy Promotion Exam, his teammate Rangobart Eck Waria Roberbad mistook them for golems.