Chemical Dropout

 is a boss monster that is always located in the last floor of each level of the Sewage Plant. Chemical Dropout can also be faced on various floors in the Deepest Ruin.

Behavior and strategy
Depending on the distance from the player, and his health, Chemical Dropout will use one of his 3 attacks: A viable strategy for this fight is to run close, and force Chemical Dropout to use his slow melee combo, instead of his more threatening ranged attacks. Directly after this would be the time to strike, before repeating the process.
 * First, a fairly slow melee combo with the Metal Jar. First a horizontal sweep, followed by a slam. These attacks have a fairly small hitbox. This attack is used whenever the Builder is in melee range.
 * Secondly, a fairly accurate sludge projectile from his gun. If you are hit by this attack, it will leave a non-damaging puddle effect on the ground. This attack is used when the Builder is outside of his melee range.
 * Lastly, a fairly accurate stream of sludge, that is only used when he is under 50% health. This stream lasts for multiple seconds, and will damage you if you stand inside it. It can be avoided by dodging precisely, or by running close to him.

Alternatively, when in Chemical Dropout's second phase, you can bait out his stream attack before running in to dish out a few melee attacks.

Trivia

 * was the third boss added to during its Alpha stage.
 * Each time the player commissions the Civil Corps to delve into the Sewage Plant, they will always bring back the loot from the, though this extra loot isn't shown to be included in their commission. If, for example, the player commissions them to run the same level three times, then they will bring three times the loot, including loot from the.