In Quake 4, the Network Guardian, also referred to as the Tower Guardian, is the second unique boss fought in the game. It is a gigantic, 30-foot tall King Kong-like alien monster that has been assimilated by the Strogg, and serves as a guardian of the 3 Towers that surround the Nexus Tower at the heart of the Strogg capital city. The Strogg insignia is tattooed or branded into his stomach area. The Network Guardian is equipped with a jetpack, allowing it to quickly fly between all three towers at will and making it an extremely effective anti-aircraft defender. It is equipped with a pair of forearm-mounted cannons; the right one is capable of firing a shotgun-like spread of several blaster bolts, while the left one is capable of firing single large guided rockets, similar to the one fired by the Heavy Hover Tank. The Guardian can also launch a single, huge MIRV rocket into the air to create a rain of small rockets that home towards the player when he is close to death.
After making several appearances throughout the Data Tower levels where it harasses the player and attacks Marine assault forces, the Network Guardian is finally fought on the roof of the Data Networking Tower, in the level Data Networking Security.
The Guardian walks slowly around on the roof while firing at the player; additionally, it will periodically use its jetpack to take to the air and fire at the player from a higher position, and it will attempt to approach the player while doing so.
The Guardian has a number of attacks that it uses against the player throughout the battle. Its two primary weapons are a blaster that fires a shotgun-like spread of several blaster bolts per shot, and a rocket launcher that fires a single, large homing warhead with an extremely large splash damage radius, similar to the primary weapon of the Heavy Hover Tank. The Guardian mainly alternates between these two weapons when attacking the player. While airborne, the Guardian can also fire a series of large blaster bolts sweeping from left to right. Finally, the Guardian can fire a single huge MIRV rocket high into the air, this rocket will fly upward for several seconds before finally exploding into a swarm of more than a dozen small rockets that will fly downwards towards the player. The MIRV rocket storm is almost impossible to dodge, although you can hide from it with some success under the doorway from which you originally entered the roof.
The Guardian can also hover over the player, doing constant gradual damage with the flames from its jetpack. Finally, it has a number of powerful melee attacks, but only uses them if the player walks right up to it while it is on the ground.
During the Guardian battle, Strogg fighter jets will periodically strafe the roof, carpet bombing along the left and right edges. This can do serious damage to the player if they are caught in the carpet bombing.
- Because of its extremely high health, conventional small arms are virtually useless against the Network Guardian. Instead, it should be fought with the heaviest weapons available, or the battle will go on for a long time. The weapons of choice are the Dark Matter Gun and the Rocket Launcher. If you are running low on these, Railgun and Lightning Gun are working well too. The Guardian's blaster bolts can be avoided by strafing or using the four mounds at the corners of the roof as cover; its homing warheads can likewise be hidden from behind the mounds, or blown up with gunfire before they can reach you, Machine Gun can be handy for shooting down these missiles, look for blue fire behind the missile because you will receive no warning when the guided missile is fired. The Network Guardian is quite agile, stay mobile and watch where you step, it's possible to fall from the roof or being blown off the roof.
- If he gets too close, use Shotgun or Hyperblaster against him. The melee attacks from Network Guardian are the most dangerous attack forms, about 3 strikes you are "out", that's another reason you want to keep a distance from it. Don't stay at one spot for too long, it's big, but it still can reach you very quickly, on higher difficulties, it will be more likely to attempt to melee you.
- Like its homing missile, you can use Rocket Launchers homing laser upgrade to improve accuracy, the guided nails also works well.
- Health, armor, and ammo are scattered throughout the roof, and you should definitely make a note of their locations to restock ammo and heal up as you take damage throughout the battle.
- You cannot harm it until its health bar appears on screen, so attack only when you can. After depleting its health to about 30% left, it will call for "air support". Ignore the Flyer which are bombard and target you, that is the only thing that are distracting you and make sure focusing on the Guardian itself. While it is impossible to face two at the same time, and the flyer attack is really hard to dodge. So its suggested not taking too much damage before the Flyers show up (you will need these medical supplies when they do). Kill the Network Guardian as quickly as you can prevent further Flyer attacks.
- It is possible to trick the Network Guardian into the Flyer's path. This will kill it with no the effort needed for the last 30% of its health.
- There is a bug, if it is killed, when the jetpack engine is on, it won't decomposition it back to processing facility. Also some of his teeth with gums will appear in the air and turn into green color as if vaporizing, but then it goes into its normal colors and repeats.
- It's considering that it size is the same as the Guardian of Hell from Doom 3, another Game which Id Software has developed.
- It's the largest of bosses in all Quake games so far.