Guardian of Hell

The Guardian of Hell (HP: 800), or simply known as the Guardian, is the second boss in Doom 3. It is seen exclusively when the player reaches the end of the Hell level. This T-Rex-like demon stands more than 15 feet tall, just a little over 2.5 times taller than a human soldier.

Appearance
The Guardian looks vaguely like a Tyrannosaurus Rex, but with larger and more muscular arms ending in large round fists that appear to contain cracks full of lava, muscular legs with hooves, a hunched upper body, a very long tail that ends with a ball with cracks full of lava in it, an armored back with traces of lava, and a head that has stereotypical demonic horns. The designers commented in the Making of Doom 3 book that it was created with the idea of a pre-human hell during the prehistoric age, and it was something that dinosaurs feared and perhaps made them go extinct.

Its refuge is a large area of Hell that is filled with large pillars of rock and slabs of demon flesh can be seen strewn on some of them.

Its primary attacks consist of punching with its large fists and pounding the ground, which emits larges spheres of energy that burst from the Guardian in all 8 directions. It can also charge at you.

The Guardian's tough hide renders it invulnerable to all forms of weapons fire.

Seekers


The Guardian of Hell is blind due to its age; what remains of its eyes are shallow pits.

It summons much smaller creatures dubbed Seekers, three at a time, to "see" for it and locate its targets. The seekers do not attack the player themselves, but they light the area and alert the Guardian to your location.

Strategy
Killing the three Seekers forces the Guardian to generate more, revealing its vulnerable spot: a glowing orb of energy in an opening of the Guardian's back. Shooting this orb is the only way to kill the Guardian. As you fight the Guardian, the Soul Cube will inform you of this weakness.

The guardian is relatively easy to kill if you can manage to avoid the energy spheres. Kill the seekers with the plasma gun or the rocket launcher, and when the glowing energy orb appears, unload your chaingun into it. This should kill the beast in 4 rounds (3 if you aim well). It is also possible (although difficult) to kill the monster using 2 charged BFG shots.

After killing the beast, the Soul Cube is released.

Unlike most other demons, the Guardian's body does not dissolve.

Resurrection of Evil
In Resurrection of Evil the head of the Guardian is engraved on some stone tablets. This could mean that either the Guardian left Hell to assist in the invasion, some of Mars' civilization saw it in Hell, there may be more than one guardian, or it was simply aesthetically pleasing to the game's designers.