Emerging from the ground, Spider Mastermind displays its prowess with four legs and a massive weapon below its head. It is well armored, with a couple of obvious weak spots at the top of its head.
Beam Salvo – When the spider flips over, it fires energy shots at a high rate of fire. Quickly move to the side and keep moving until the attack stops. It can fire this weapon from either side, changing up the angle of the energy shots.
Laser Beam Sweep – Watch for it to plant its two front claws into the ground. Three lasers shoot out each side while a seventh fires from its gun. It sweeps to one side and back, alternating low/high or high/low. Hop over the low beams. You can easily crouch beneath the high ones.
Side Step – The boss has the ability to move around the area quickly with a side step and hop. It can fire its energy gun as it does so.
Claw Swipe – Be careful when close to the behemoth, as it swipes its claw. Stay well clear of the boss to avoid getting hit.
Gas Cloud – About halfway through its health bar, the boss moves to the corner and launches a gas attack, which inflicts damage if you get caught up in it. When it bends over, quickly climb onto one of the pillars that appear around the battlefield and fire a high-power weapon at the boss. Be careful that you do not blow up your own platform.
Chain Beam – Once the electrified ground is removed, hop down to avoid spikes that shoot out from the top of the pillars. The demon sends a beam between the pillars that detonates the rock formations, so be careful. Destroy the first pillar before it charges to stun the boss.
Collapse - When Spider Mastermind’s health gets to critical levels, it collapses to the ground. It retains the ability to shoot its energy gun and lasers, but with limited mobility.
Telekinesis Throw – Be ready to dodge out of the way as it raises a pillar above its head and throws it your way. Destroy the pillar before it’s fully charged to stun the boss.
Pillars pop out of the ground, giving you a little cover as you fight the behemoth, though these are easily destroyed. Don’t spend too much time behind one. Note that the pillars can contain health and ammo. If you’re low on either, you can sacrifice some temporary cover to replenish.
Hitting the boss with the BFG causes it to collapse to the ground for a short time. Quickly pull out one of your more powerful weapons, such as the Gauss Cannon, and light the creature up. Resources spew out as you do so. Look for BFG Ammo as it spawns around the area.
Concentrate your weapon fire at the boss’s brain until it finally falls in dramatic fashion. Move in and perform a Glory Kill to finish it off.
Note that you get bonus weapon upgrade points whenever you kill a boss (6 points) or destroy VEGA (5 points).