Why the Chaingunner, Revenant, Arch-Vile and Spider Demon are not present in this installment.
The Mother Demon may have been pressed for time and resources to launch the surprise attack and couldn't resurrect the most powerful enemies or didn't have time to.- The Chaingunners — being Former Commandos — were in short supply or overlooked due to time constraints.
- To be just, the chaingunners only appeared on Earth (possibly elite members of the army) and this story takes place on Mars and Hell itself. As the first game.
- The Revenants — being already dead and decayed — were probably beyond recovery due to decay and there was no time to conscript and arm a new generation of Revenants from the fresh dead.
- Arch-Viles — being more complex and intricate beings — were unable to be resurrected just as Arch-Viles may not resurrect their own kind.
- The Spider Masterminds were deemed Awesome, but Impractical experiments in cybernetics, due to the sheer size and lack of tolerance of pain.
- As a result, the Mother Demon made upgrades to the Arachnotrons, enhanced the Pain Elementals, and brought heightened aggression to the Lost Souls to compensate for the loss of some of her heavy soldiers.
The Mother Demon and Sister Resurrector both lost their resurrecting powers from reviving all of the demons for the events of Doom 64...at least temporarily.
Considering not all of the monster types returned and all of the resurrecting required, it's possible that their magic energies were largely depleted and required replenishment. However, with Doom Guy / Slayer responding to the invasion very rapidly, the sisters had to fight without being fully recovered.