The Destroyer

The Destroyer is a massive, godlike being from another dimension, and the final boss in Borderlands. It is a mass of flesh with a huge, glowing eye, a massive mouth, and several tentacles. The Eridians imprisoned the Destroyer within the Vault thousands of years previously at the cost of their entire civilization, in order to prevent the monstrosity from consuming the universe.

Background
The Guardian Angel knows of The Destroyer and that it is what awaits those who open the Vault. However it chooses not to share this information with the player characters, likely because it fears they would not pursue the Vault if they had prior knowledge of its contents. The Angel appears to want to use the Vault Hunters to defeat the Destroyer once and for all.

Combat
The Destroyer does not move throughout the battle. It has multiple weak spots: Its eye, the glowing spots on the tentacles and its mouth/tongue. The Destroyer has a truly prodigious amount of health, as befits an extra-dimensional, godlike being of destruction. But ultimately the battle is relatively easy.

At the beginning of the fight, and throughout the battle, the Destroyer will sprout a set of purple tentacles with glowing orbs near their bases. These tentacles throw purple, explosive spikes that can arc over cover, thus it is imperative to destroy these tentacles when they appear. When the spikes explode, they drop ammo which can be useful if a character is running low. They can be destroyed by shooting the glowing orbs near the bases of the tentacles. These tentacles also count as separate enemies; severing one of them will activate 'On Kill' buffs and can trigger a second wind.

The Destroyer will also lash out with its reddish tentacles. These can't be destroyed, unlike the purple ones, but these attacks are fairly obvious and easy to avoid, and only happens occasionally in any case. More often it will lift its red tentacles into the air and slam them into the ground, releasing a shockwave that launches nearby characters back. This can be avoided by hiding behind any of the stone pillars that litter the battlefield.

As the battle progresses, The Destroyer will also unleash a concentrated blast of pure energy from its glowing eye. The charging of this beam can be heard before it is unleashed. This is a very damaging attack and is difficult to dodge, but it can be avoided by hiding behind most of the rocky pillars. This attack is used frequently as a follow up to its tentacle slam, so be sure to avoid both, or your character may be knocked away from cover and unable to reach it again when it unleashes the beam. The beam attack also has a large amount of knock-back, so attempts to stay in the back of the area, out of range of some of its tentacles, can result in being knocked off the cliff. Sometimes the beam can be seen piercing a pillar, although the stone will block the damage regardless.

If your character is crippled, look above and to the left of the Destroyer. Rakk sometimes spawn in the sky here and are good targets for a Second Wind. Second Wind can also be activated by destroying one of the vulnerable tentacles.

Time can be saved by finding where the tentacles wrap around the pillars of stone, and attack at close range or melee. It will take a while to whittle the Destroyer's life down in this manner, but it's much faster than playing hide and seek against The Destroyer's formidable frontal attacks.

One strategy involves using a burst fire combat rifle, hiding behind one pillar, peeking out every now and again, popping it in the eye and taking cover when it attacks. Using this method can allow a very easy victory without taking many (if any) hits.

A health regenerating shield is advised.

After a substantial amount of damage, The Destroyer will finally be defeated. Enjoy the ending and go on to Playthrough 2!

Strategies
These strategies will work with any character, but high accuracy or bullet regeneration is recommended for the second:

If at this point in the game you have any Eridian weapons, equip them and use either them or an assault rifle to take down three of the four purple tentacles (leave one to stop the rest respawning.) Now just fire away while hiding behind the stone pillars for the duration of the eye attack; this should allow you to kill The Destroyer with ease and without you having to worry about ammo. An extremely effective weapon is the Eridian Thunderstorm. While it recharges, just use another weapon to take the purple tentacles down.

Make certain you destroy the purple tentacles whenever they appear. Stand behind one of the large rocks that has a half circle removed from one side. Through this, if you are careful, you can have shooting access to the eye. You will only have to worry about the slam, as the beam will not be able to penetrate the rock, and The Destroyer is unable to aim for anything but the center of your body; which is behind a rock. You will be safe, and have an easy avenue to The Destroyer.

An extremely effective weapon against The Destroyer is The Boom Stick, especially if you have a increased clip size via class mods or skill tree. It's fast fire rate, high damage, make it extremely effective. It's spread is also somewhat negligible against this huge target.

Another strategy is to move to the left side of The Destroyer itself, this will prevent it from attacking your character, making it very easy to kill if you have a means of ammunition regeneration.

It has also been reported that running up and throwing multiple MIRV grenades into the destroyers mouth can result in an easy kill. This can also be done with a fast-firing rocket launcher or shotgun-rocket-launcher.

In addition, using a scope to aim a Longbow grenade into the destroyers eye will result in the grenade critically hitting the destroyer, with 7 grenades being able to take roughly a quarter of its life.

Hunter

 * If you wish to be a sniper, get yourself a sniper rifle, get a sniper rifle ammo regeneration mod (for when you run out and there is an extremely high chance you will).
 * Once the battle starts head to either left or right (it doesn't matter just get in the general area of one of the 4 main pillars near the boss).
 * Take out three of the purple tentacles that throw the explosive spines.
 * Leave the fourth one, if you somehow after destroying three of them manage to get taken down you can use the 4th one for your second wind. Don't destroy that fourth one throughout the battle (as long as the last one doesn't die the rest won't respawn.)
 * Once you've destroyed the three of the purple tentacles you can spend the rest of the fight concentrating on the eye. With 5 points in CALIBER, DEADLY, and mod that either increases critical damage, or sniper rifle damage (like a +caliber sniper mod/+deadly gunslinger mod).
 * With five levels of Lethal Strike the hunter will do 233 damage, or 5000 damage for a critical hit. This can be used after the Destroyer wraps its tentacle around the first rows of pillars.
 * This battle will progress REALLY quickly (in the area of about 2 minutes) if you have the Jakobs Skullmasher sniper rifle, they do in excess (with applicable mods/skills) of 15,000 per critical hit.
 * Also, if you stand back near the New-U station, you can unload a assault rifle (or anything else that has a decent accuracy) into The Destroyer's mouth. I did this using an assault rifle with a damage of 100, and it took about 300 or 400 bullets, but it works.
 * If you wish to do it as a gunslinger, an ammo regeneration mod is again recommended.
 * If you have a large clipped repeater and a high rate of fire, you don't need to worry about getting criticals, just fire away from behind the pillar until he is dead.
 * As most high fire rate and large clip repeaters are not particularly accurate anyway, focusing on the critical locations can leave you vulnerable. Instead, just aim in the general direction.
 * It can be killed with about 800 pre-modified shots from a ~60 damage repeater. It will take many more if you don't have Gun Crazy and Hair Trigger. Critical hits happen regularly enough from scattered shots.
 * Your Bloodwing will hit the Destroyer's mouth if you are close enough. Explosive is the only element that is effective.

Soldier

 * For an assault rifle gunner, equip ammo regeneration of any kind, be it a gun, a class mod, or skill. Take cover and fire, throwing a Scorpio Turret whenever it's ready.
 * For a Shotgunner, move into close range if you have a soldier medic on your team.
 * Overload is a useful skill to bring to this battle.

Glitches
Pertaining to the battle

A glitch exists where characters can sometimes be walked onto the Destroyer's platform, passing through its model-texture, and thus are able to walk inside its body. This is not a very significant advantage, however, since the projectiles it fires can still reach and harm the character, as do any internal movements made by its tentacles. All damage dealt to The Destroyer is still done on the surface of its model-texture, so you would still have to aim at particular areas, such as its eye, if you wanted to deal a critical hit. The only real advantage this glitch has is if you have a highly inaccurate gun, or explosive weapon, and want to deal flat damage to it without the chance of its tentacles getting in the way.

It is unconfirmed whether or not its eye beam attack can still hit you in this glitch.

When fighting The Destroyer walk behind the quick travel station nearest to the wall and crouch down, the eye beam attack and tentacles cannot attack you, depending on how close you are to the spot the projectiles can or cannot hit you. From here continually shoot at the eye. you may get lucky and tentacles that fire the projectiles may stop appearing and you may begin your assault on the eye.

(This isnt a good critical hit spot) Also another strategy is at the begining run all the way the the right or left edges in the back and crouch too. So when the arms stretch out to the poles you are kind of stuck in a little triangle.(NOTE:Brick's class works well for damaging it,Mordecai is good for stunning it, Roland is good for the Scorpio turret,and Lilith isnt good in that place.) So now go under the arms that stretched to the pole so the explosves dont hit you. (An ammo regeneration mod or weapon is best to use.) So stay there for the rest of the battle and spam all the bullets you want and you'll never get hit or miss. GOOD LUCK! :)

Pertaining to Death

If you are knocked over the cliff in the back of the area, or simply jump over it of your own accord, (both of which will result in death), The Destroyer will have the same amount of health as it did before you died. This is contrary to a normal, bleed-out death, where The Destroyer will have full health once you respawn. The same situation has been reported to happen when both players die from normal, bleed-out deaths on co-op mode.

Bugs
Some players have experienced a bug that caused The Destroyer to vanish from play when one player has exited during the fight with the Destroyer. Upon a restart of the game the Destroyer is absent, the mission checked as complete and the Vault Key unobtainable. This could have been caused by a game crash during the fight in some cases.

Workarounds found so far:
 * Connect to friend's game and kill The Destroyer in co-op.
 * Hex edit the save file. How to do so is described here: Borderlands discussion on Steampowered games

Trivia

 * The Destroyer is very similar to the final boss of Gearbox Software's first game, the Half-Life expansion Opposing Force.