Hell Knight/Doom 3

The Hell Knight in Doom 3 is very muscular and heavy. An in-game examination of their spine indicates they have massive skeletons as well. They have no visible eyes, ears or nose. It looks rather different from the old Hell Knight, as it doesn't have any horns, hooves and doesn't look anything like a goat, but its overall body structure is similar, albeit a bit more powerful.

Their attacks are very similar to the Imp: melee attacks (including biting) and aquamarine fireballs with splash damage. The Hell Knight, however, doesn't have any sudden leaps and its fireballs have a wider area of effect. When facing one of them, it is strongly recommended to use the Soul Cube or the BFG, for they can absorb large amounts of damage.

The Doom 3 Hell Knight is actually a mixture of the original Hell Knight and the Classic Baron of Hell, being tougher than the original Hell Knight, but a little weaker than the old Baron (It takes between four to five direct rocket hits to kill it). It is possibly for this reason that there is no Baron of Hell in Doom 3.

The first Hell Knight's appearance was in Delta Labs 4. Two of them appear in a relatively open room where a portal opens and 2 Hell Knights come from. This might be a reference to the first bosses in the original Doom, where the player must defeat a pair of Barons of Hell at the end of Knee-Deep in the Dead. These two Hell Knights are tougher than those encountered later in the game, able to survive a fully charged BFG blast.