Crawmerax's Lair

Crawmerax's Lair is an area in The Secret Armory of General Knoxx. You go here when you get the mission from the T-Bone Junction Bounty Board entitled "You. Will. Die.", which requires you to kill Crawmerax the Invincible.

Crawmerax is a large boss modeled after the crab worms earlier in the game. He supposedly drops the best weapons and loot out of all the bosses. Crawmerax can be killed by shooting the purple spots on his back, 2 claws, and eye. Crawmerax is incredibly difficult to kill, even on playthrough 1, and usually requires 4 people to take down. It will regenerate all of his health if everyone dies, so one person must always be up on the field. The best strategy for this is to have one person hide on the left side, behind the ledges. When behind the ledges, Crawmerax will usually not bother you, and cannot hit you with most attacks. This strategy allows the other people to die and respond without having to kill the boss all over again. Crawmerax is weak to the electric element, so they are advised. Also weapons with high rates of fire allow the most critical hits in the smallest amounts of time on his weak points. Note that Crawmerax cannot be killed unless he is hit in the weak points. Crawmerax has several other minions that go around the field trying to kill you.

Crawmerax is the boss most likely to drop ultra-rare 'pearlescent' weapons, which are significantly more powerful than orange tier weapons. After killing Crawmerax you get a 50g Achievement named 'Vincible' alluring back to Crawmerax the invincible. You also finish the quest "You. Will. Die."

After completing the quest, It is still possible to fight Crawmerax, allowing for constant farming by groups or determined individuals.

Trivia

 * The road signs leading to this area are labeled "Secret Final Boss", and can be found as far away as on the Crimson Tollway, perhaps further.