Hell Knight/Doom 3

The Doom 3 Hell Knight, in many ways, is vastly different from it's original predecessor. It takes the appearance of a tall muscular alien or mutant, rather than a satyr or minotaur. An in-game examination of its spine indicates it has a massive skeleton. It has no visible nose, and its deformed ears resemble a human's, fused to the sides of its head. Its obscure eyes are very small and black, located on the sides of the head just above the mouth. Characterized by it's low-pitch guttural breathing and growling, It is easily the tallest non-boss enemy in the game. Assuming the Marine is 6 feet (1.8m) tall, the Hell Knight stands about 10 feet (3 meters) tall.

In Hell, Hell Knights show a different appearance from those on Mars. Their skin is greyish-green and some parts, such as the mouth, upper chest, hands and feet, are red, possibly soaked with blood. They are covered with scars and demonic runes, and have a pentagram on their forehead.

Aside from it's appearance, The Hell Knight also serves as one of the game's most elite-leveled enemies, making them in par with the Baron of Hell in the classic games.

It's introductory cutscene features The Marine arriving at the main teleportation room in Delta Labs Sector 4, where he witnesses the portal to Hell being opened under Malcolm Betruger's supervision. A biosuit-clad scientist emerges from it, followed by a huge Hell Knight right behind him. The scientist pleads for his life, but the Knight grabs and throws him violently against the machinery of one of the portal generators, presumably killing him; a second Hell Knight comes out from the portal and then both monsters charge towards the Marine.

Combat characteristics
The Hell Knight's attacks are similar to those of the Imp's: it hurls bluish green fireballs at long range and substitutes to clawing attacks at close range. However, it lacks the ability to leap and its clawing attacks are not instanteous like the Imp's; the lag to initiate their melee attack is around 1-2 seconds. To make up for it's lack of agility, the Hell Knight can launch a powerful biting attack, allowing them to hit further than it's clawing, although it also suffers from the same lag duration to initiate it. The green plasma balls it throws are much larger, more powerful, and have a wider area of effect.

Tactical analysis
The Doom 3 Hell Knight, in many ways, is a lot tougher than it's classic version would otherwise prove, as it has nearly equivalent hitpoints of the original Baron of Hell, while the original Hell Knight had half the amount.

it is strongly recommended to take out Hell Knights from range. The Rocket Launcher, Plasma Gun, Chain Gun, are very effective weapons to take them out. It can take 4-5 rockets from the Rocket Launcher and close to a full magazine of the Chain Gun and Plasma Gun to kill one, but their large stature and slow speed makes targeting headshots easier, in which fewer shots are needed to finish them off. If the situation permits, the Soul Cube and BFG is an excellent choice.

The Hell Knight, despite being deadly, is also quite slow and avoidable with it's attacks. You can get up close range and unleash your Shotgun couple of times while actively backing away to avoid their clawing attacks. However, be careful as they can also bite, which allows them to hit you further than its claws.

At range, it is a very bad idea to retreat from one when the monster is about to throw a fireball, as a direct hit can do grievous damage. Fortunately, its fireballs are very easy to dodge, as the Hell Knight's height means they are launched from farther up, making it possible to literally run under them. However, take caution to not get yourself cornered in enclosed spaces as their fireballs can do significantly high damage from the splash damage.

The expansion pack and the additional content of the BFG edition introduces two new weapons to even out the odds against the Hell Knight. The Grabber is a relatively effective weapon, however it requires 5 direct volleys from and back at the Hell Knight to vanquish it. The super shotgun is also relatively effective, provided the player has sufficient space to keep dodging, firing and reloading.

UAC research notes
These notes can be downloaded to the player's PDA during the course of the game:

Specimen 31 - Hell Knight (partial)

''The cranial mass of this bipedal specimen indicates that it is one of the largest creatures inhabiting the site. Overpowering its prey with sheer might, the Hell Knight is one of the most ferocious predators known to our researchers. Like the Imp, this creature is able to defend itself at long-range with thrown plasma projectiles.''

Doom Resurrection
The Hell Knight is a boss in Doom Resurrection in the fourth chapter, inside the Delta Labs. Its only attack is to throw green energy balls at the player, which can cause quite a bit of damage. They can be dodged like a usual Imp's energy ball. After draining its health, it will push the player into the Hellgate to end up being sent to Hell.

Trivia

 * Considering that the Baron of Hell is the only non-boss monster from the first Doom game that was never featured, the Hell Knight likely serves as Doom 3's official representation of that monster over it's classic namesake, which only appeared in the second game.
 * Aside from having nearly equivalent hitpoints, the Hell Knight's introductory cutscene takes inspiration from a pair of Barons of Hell as sub-bosses of Doom' s first episode.
 * In the later game, the Hell Knight is introduced as a middle-tier monster like in the classic games (only faster and limited to melee), while the actual Baron of Hell is more faithful from it's classic iteration as a very powerful demon that can shoot fireballs and melee, like the Doom 3 Hell Knight.
 * If one uses the noclip cheat, a stream of saliva can be seen running from the Hell Knight's mouth.
 * Like the Mancubus, the Hell Knight is characterized for it's loud banging footsteps and it's ability to shake the ground while walking.
 * The Hell Knight is featured on the cover art of the game.