Mother Demon

The Mother Demon is the final boss of Doom 64 and is found on MAP28: The Absolution.

A monstrosity in her own right, the Mother Demon appears as a large demonic larva with dead black eyes with red irises, four arms, a skull-like face and smallish mouth filled with many long, sharp teeth. It has no wings, yet moves by floating around above what appear to be vestigial legs. She makes a soul-chilling cry of discovery upon being roused, a ghastly snarl when moving about and a frightful shriek like a Banshee when she is damaged.

The Mother Demon's attack consists of powerful flame trails, followed by a set of 4 homing fireballs which split up when they hit something.

In the backstory, the Mother Demon appeared in an old relay satellite, battered by neutrons and quarantined by massive levels of radiation. When her presence was made, the satellite activated and sent a message to Earth. Her presence came with many demons and though their energy signatures were caught, the Mother Demon used the radiation levels to escape detection. She has rejuvenation powers and whenever she walked by a corpse of a demon, it was systematically brought back to life. It also made them stronger than before.

After she is killed, the Marine decides to remain in Hell to ensure no demon ever rises again.

Tactical analysis
The Mother Demon will kill you quickly if you come in battle unprepared. Her flame trail, when hit, launches you into the air, making it harder for you to control your movements. At the same time, she will launch 4 homing rockets at you, being the only monster to perform 2 attacks at the same time. Even though 1 Homing Missile is not as strong as 1 Rocket, getting hit by 1 of them will bounce you back pretty far and getting hit by all 4 of them at once can be fatal regardless of your health and armor levels. Dodging the rockets can be a hassle (though you can still hide on the walls like how you fight the Revenant), especially when hit by the flame trail or the first rocket. Beware of the homing rockets though, as once they explode, they will send out a barrage of smaller fireballs in all directions.

She is the fastest demon in Doom 64, moving just as fast as the player, and can catch up to the player in seconds, unless the player is using the neutral position reset which makes the player run extremely fast.

The most effective way to defeat the Mother Demon is to use the fully-equipped Unmaker. Not only will the Unmaker do a lot of damage at rapid-firing speeds, but will also stun her to prevent her from using her 4 homing missiles. She will still attack with the flame trails as the only attack to avoid. Under suppressed fire from the weapon, she will die very quickly.

However, if you did not receive all 3 of the Demon Keys needed to fully equip the Unmaker, the battle against the Mother Demon is very difficult. To make matters worse, varying upon how many keys you collected if you did not collect all 3, your previous battle before facing her may have consumed a lot of ammunition. Your only real choice is to use the BFG 9000, but it requires precise timing and a lot of Plasma Cells conserved from the previous battle against the horde of enemies. The Rocket Launcher is the next best alternative, but defeating the Mother Demon with it takes longer and is more difficult; surprisingly enough, the Mother Demon is not immune to blast damage, taking around 25 rockets to kill.

It is also possible to kill her with the Super shotgun, by running up to it and shooting you will stun her, she will then use her flame trail that can be easily avoided by side stepping a little, by this time you will be able to shoot her again and stun her again, by doing this you can prevent her from launching her homing rockets and killing her without much problem, it is recommended that this tactic be used by experienced players, since the timing to close up to her and fire without giving her the chance to fire the homing rockets is very small, and the sequence of shooting and side stepping takes a little practice to master, but once the sequence starts, killing the Mother Demon is extremely easy, it takes 42 Super shotgun shots to kill the Mother Demon

Other games
There is a possible reference to the Mother Demon in Doom 3. When the player opens the PDA after obtaining an audio log in the Dig Site, there is a mention of a demon that is said to have given birth to all other demons, though the demon is actually never seen in the game.

In Doom 2016 in the main room with the tanks filled with demons and in the room behind Dr. Olivia Pierce's office where you can find the Soul Cube (which is unusable) and the hologram of the Doomslayer's tomb along with his suit, you can find a fetus version of what looks similar to the Mother Demon. These creatures are located in the tank closest to the Soul Cube but does not move or attack as she is not fully grown. These appear to be immature versions of the gremlin or the abaddon pilot seen in the Art of Doom, but those creatures especially one form of the Abaddon Pilot look to be inspired by Doom 64 Demon Queen.

While this thing doesn't look exactly like the Mother Demon, slightly different head. It does appear to have evidence of multiple arms in development possibly four.

The final boss of Half-Life, Nihilanth, greatly resembles Mother Demon. Like Mother Demon, Nihilanth has multiple arms, vestigial legs and an oversized head, and attacks with volleys of homing projectiles.