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Outriders' endgame revolves around Expeditions, time-sensitive dungeons that grant better rewards as you clear the mission faster. Builds that output a lot of damage are preferred for every Expedition, but some Expeditions are far easier than others.
Chem Plant is one of the easiest Expeditions in the game. Nearly every build can clear this mission in a short timeframe, although the removal of timers has made this mission much less stressful. If you're looking to unlock Challenge Tiers or farm legendaries, this is a great Expedition to farm. Here's a guide on how to quickly clear the Chem Plant Expedition in Outriders.
Updated November 29th, 2021, by Charles Burgar: New Horizon has removed timed Expeditions from Outriders altogether. Any build, regardless of clearspeed, can now finish Expeditions and receive excellent rewards. We've updated this guide to include updated rewards from Chem Plant and some excellent skills and mods that should make farming this Expedition much easier.
Completion Times And Enemies
Most of this level consists of Insurgents (bandit enemies), although the last arena is mostly against Warzone Beasts. Many of this level's enemies are heavily armored, so consider bringing Anomaly damage or Armor Piercing mods to take down these enemies quickly. Enemies pack quite a punch once you reach the interior sections of Chem Plant, so equipping any mods that enhance your Armor is recommended.
Recommended Skills And Mods
Devastator
An Anomaly build will wreck shop here. Gravity Leap is a great idea since the arenas in this Expedition are medium-sized. Golem is also a safe choice if you're playing at a higher CT than your character can typically handle.
Pyromancer
There's a decent bit of cover in this mission, so you can get away with using a longer cast skill like F.A.S.E.R. Beam or multiple charges of a certain skill. Really, anything works here. Ash Blast and Overheat is still a meta combo with the New Horizon patch. It can one-shot most waves with the right gear.
Technomancer
It's hard to top Blighted Rounds on a Technomancer. Pair the skill with Cold Snap and maybe Blighted Turret to deal some excellent damage.
Trickster
Twisted Rounds and Hunt the Prey work well here, allowing you to close the gap before delivering a killing blow. If you're an Anomaly build, Temporal Blade can deal some serious damage to these enemies.
Mods
A shotgun with Shadow Comet or any AoE mod can easily hit multiple targets in this mission. Quite a few enemies spawn atop each other, making it easy to proc these mods multiple times in one shot. Beyond that, Mitigation from Death is highly recommended for non-Devastators since it gives so much armor.
Opening Encounter
Right as the Expedition begins, head up the set of stairs to your left to take out the Marksman sniper. From there, eliminate the fodder enemies as you make your way to the gate. They shouldn't pose much of a threat.
Juggernaut Captain
When you get near the gate, a second wave of enemies will begin to spawn. To the right of the gate will be a lone Juggernaut Captain that can inflict Freeze and has an absurdly large health bar. Take this enemy out immediately, using all of your abilities to nuke its health bar. Anomaly damage will bypass most of its armor, although you'll still need some good damage scaling to quickly kill this Elite. If it does end up Freezing you, use your melee attack. Your melee ability breaks you out of crowd control effects.
Past the Juggernaut will be a handful of fodder enemies, including Breachers and Rifleman. Carve a path through them, then interact with the switch at the end of the path to enter the chemical plant.
Chem Plant Interior
Right as you enter the chem plant, head left to take out a small group of Insurgents. The Captain is your top priority here. When those enemies are dead, you'll have a group of Breachers and Ironclads charge up the stairs next to you. Either stick to cover or push them. There will be a few stragglers on the other side of the room, likely moving to your location. Take them out to spawn the next wave of enemies.
Second Wave
A massive wave of enemies will spawn together directly across from where you came from, consisting of a few Captains and a Juggernaut Captain. Try not to get hit by a melee unit when fighting these guys. All of these enemies come in at once in a massive cluster. If you have any AoE weapon mods or skills, now is the time to use them. Kill the Juggernaut as fast as you can to prevent getting Frozen. Once all of the enemies are defeated, run down the nearby stairs to reach the next combat arena.
Chem Plant Second Floor
This room is the hardest part of Chem Plant. Right as you enter this room, you'll want to either enter the room to your right or rush the Juggernaut Captain in front of you. Once again, these Juggernaut Captains can inflict Frozen on you, resulting in certain death at high Challenge Tiers. Focus on defeating the Juggernaut Captains when it's safe.
Most enemies will stick to the right side of the arena, so you should stay there if you want to complete Chem Plant quickly. Killing most of the enemies will cause enemies to spawn at the left side of the room. Take them out, then interact with the elevator at the end of the room.
Second Wave (And Encounter Skip)
Two waves will spawn simultaneously, one directly across from you and another to your right. To progress, you're supposed to kill both waves. However, you can skip half of this encounter.
You only need to kill one wave of enemies to open the elevator door. Kill the wave directly across from you, as the other wave is made up almost entirely of Elites. When that wave is dealt with, you'll hear an audio queue after a few seconds. That queue tells you that the elevator doors have opened, allowing you to escape. Run to the elevator to reach the boss arena. If you don't want to skip this part, simply kill the second wave before leaving.
Reactor
Dispatch the small group of Insurgents guarding the reactor, then interact with the reactor's terminal to start the final encounter. Warzone Beasts will make up most of the enemy roster down here, so have a few crowd control effects at the ready. Enemy waves will spawn from different directions in the arena. You can either rush the enemies or stay at a distance. Use whichever strategy your build prefers.
Defeating a few Beasts will cause some Insurgent waves to spawn. Once they're taken care of, the final boss will spawn alongside quite a few Warzone Beasts. Your cooldowns will reset when the boss spawns, so feel free to use your abilities before that point.
Brood Mother Boss
Chem Plant's final boss is a Brood Mother with a massive health pool, guarded by multiple Warzone Beasts. Your cooldowns are reset when it spawns, so give the Brood Mother everything you have. You'll need to kill every enemy to complete the Expedition, so focus on the Brood Mother first before it starts to buff the other enemies. Besides the boss, multiple Perforos and Venemous variants will rush you. These enemies won't pose much of an issue. Kill all of the enemies to end the Expedition and receive your loot.