This is a guide for people new to Plague Star or those needing a refresher. It covers surface-level details to get you up to speed on how to best contribute and is based on past occurrences of the event. Don’t be surprised if changes are made when it goes live tomorrow.
-What Is It?-
Plague Star is a time-limited operation on the Plains of Eidolon on Earth where you fight off the Infested horde. It functions like a standard bounty with rewards offered in their own unique standing.
-Why Do It?-
Plague Star is famous for having some of the best rewards of any event in the game and has NO standing cap, meaning you can farm the entire day. Aside from being able to purchase ALREADY BUILT Forma, it has top-tier Zaw parts, rare arcanes, a brand new weapon, and Cetus resources that you probably shouldn’t buy because did I already mention Forma?
Plague Star has historically had relics in its reward pool and I believe it’s confirmed you can get some – if not all – of Nidus Prime’s parts from these drops. That’ll be TBD.
-When’s It Happening?-
It starts during the Sep 8th update (no exact ETA yet) and will go until Sep 30th.
-What Should I Do Beforehand?-
Unlock the Plains of Eidolon. If you don’t have an Archwing Launcher, you’ll really want to have one ready.
Farm some generic resources in the Plains. You’ll want them to construct certain gear items.
Go to your clan’s Bio Lab and make sure to research the Infested Catalyst and then add it to your gear wheel. It takes 24 hours to research.
Titania is a good frame if you already have her, but she takes a bit of a Forma investment to make sing. She is by no means required.
-How Does the Event Work?-
Go to Konzu by the main gate to start the bounty. It runs independent of day/night cycles on Cetus and comes in four stages.
 In the first stage, you will need to find a Thrax Toxin in one of the caves. Literally just find it and click. Stage over. If you’re not familiar with the caves, best to hang back and let someone else do it, as usually everyone assumes the first person in will get it and they won’t follow or help.
 In stage 2, you take the toxin to an armored vault and defend it for three tedious minutes. You will add two types of ingredients from your gear wheel to increase the difficulty and rewards of Stage 4, which we’ll talk about below. Other than a (theoretically fixed) bug with a unit that could one-shot the cart, this stage shouldn’t pose a problem.
 In stage 3, find and escort a drone to a big boil. See “What Frame Should I Bring” for tips on this stage.
 In stage 4, fight a bunch of Infested and a boss monster called the Hemocyte (up to 4 times). More on this stage below. When finished, head back to Cetus for that juicy, juicy Forma.
-What is a Hemocyte?-
A Hemocyte is a reskinned Lephantis, the boss that you farm to get Nekros. It is a huge infested enemy with three heads. Each head opens up periodically to attack, and when it does, you shoot the head to blow it up. It is totally immune to damage outside of these weak spots. Blow up all three heads to win.
One important note: both the Lephantis and the Hemocyte have a damage cap. For this reason, snipers and high damage, single-shot weapons are ill advised. We’ll talk more about this below.
-What Were Those Mixtures You Talked About?-
During the Stage 2 of the bounty, you will have the chance to add up to four Infested Catalysts and four Eidolon Phylaxises to the mixture cart. Simply walk up to the cart and click the item on your gear wheel (assuming you built and equipped them beforehand). Anyone can contribute any amount, and while etiquette dictates that each player should donate one of each, experienced players should have enough resources to contribute multiple and likely will of their own initiative. Last time folks weren’t so stingy about this as they were when the event first occurred.
As mentioned, the Infested Catalyst is researched in your clan’s Bio Lab. The Eidolon Phylaxis, however, is a reward item from this event, so if you’re brand new, you won’t be able to get it for a few runs. Don’t worry too much about it if you can’t. MOST players won’t care that you can’t contribute.
These items must be built in your foundry and added to your Gear wheel beforehand. They are treated as consumables, so try to built a whole bunch so as not to run out.
Each Phylaxis contributed during the armored vault stage raises the level (and rewards) of the Infested enemies. Each Catalyst adds another iteration of the Hemocyte boss, causing multiple to spawn. While you don’t NEED to max these contributions, when going pubs expect that to happen.
-Isn’t It Faster Not to Fight the Hemocyte?-
Some players believe the best way to farm standing is not to fight the boss at all, and therefore not contribute any of the Infested Catalyst. When that happens, you only fight a bunch of generic Infested in Stage 4, skip the boss(es) entirely, and ultimately make the last stage go by super fast. This is a quicker method with a lower payout. While this is a viable option, expect pubs to spawn the bosses.
-Why Is There a Big Boil Thing?-
It’s where the boss spawns. Don’t stand directly on it. It’ll kill you.
-Tell Me More About The Hemocyte-
The Hemocyte is invulnerable to status effects (such as Radiation/Cold/Magnetic/etc) but not most Warframe abilities, which we’ll discuss in the next section. It also comes with a lot of armor which can be stripped. I’ll mention some common methods for that below. It drops the Hunter mods as a reward on death, which range from “super useful” to “niche”.
Each head has a unique attack that you have to see for yourself, but they’ll basically either spit something or swing a big axe.
If you get too close to the thing, it will try to stomp you. When it does, all of its mouths close, meaning your teammates can’t damage it for a few seconds. For this reason, stay away from it so you can maximize the time its heads are open.
-What Frame Should I Bring?-
Titania is the Queen of Plague Star. As mentioned, the Hemocyte has a damage cap, so her fast-firing Dex Pixia in her pixie mode can absolutely shred it in seconds, assuming they’re modded well. Her flight also puts her above the Infested threat and allows her a clear shot. She also has some CC in her kit, if you want to be the only person who has ever used Titania for anything other than her 4.
She’s far from the only viable frame, however. Speeding up the drone in Stage 3 is useful to blitz through that part, and things like Nova‘s portals, Loki‘s switch teleport, and Wisp‘s wisps are all viable options.
Because the Hemocyte can be affected by certain Warframe abilities, frames that can freeze it in place can SITUATIONALLY be very useful. Rhino‘s Stomp, Nova‘s Molecular Prime, and Harrow‘s Condemn are good examples. When timed properly, they can keep one or more of the Hemocyte’s mouths open in a frozen state, giving you ample time to burst it down. When timed poorly, however, you may wind up keeping the mouths in a closed state, which drags out an already boring fight.
The Infested have tons of toxic damage, and while usually not necessary, Oberon and Trinity can contribute to keeping people alive if you’re more comfortable with them.
While these are some of the more popular options, don’t worry too much if you don’t have a “meta” frame. You can still contribute just fine as long as you know the mechanics and bring a suitable weapon.
As far as modding goes, things that protect against knockback damage are useful. Anything that heals you is also helpful given the heavy toxic damage. Otherwise no need to overthink it.
-What Weapon Should I Bring?-
There are too many to mention and I don’t want to start a flame war. Just remember that because of the damage cap, the key is something fast firing and with a high crit rate. The Soma or Grataka are perfectly acceptable low MR options, though better options exist at a higher MR. The Synapse and Pryana Prime were big names last time. Whatever you do, mod for crit. I’m sure there will be ample recommendations elsewhere, but just remember that snipers/bows/Opticor aren’t ideal. (Conversely, many beam weapons are quite strong.)
-Tell Me More About the Rewards-
When you’ve finished a run, find the mask-selling kid in Cetus where you can start ranking up a new standing called Operational Supply. Unlike other standings, it isn’t total ass to rank up.
If you don’t have the Eidolon Phylaxis blueprint, you should purchase it at Rank 1, build it, put it in your gear wheel, and contribute. Be a good teammate.
Otherwise, the best reward is Forma. You can run the event as many times as you’d like and get a buttload of standings to trade in for already constructed Forma. As mentioned, there is no daily standing cap.
There is a new weapon known as the Ghoul Saw. At the very worst it will be time-limited mastery fodder, so get it if you can.
If you don’t have them, the Zaw parts can be used to construct some of the best melee weapons in the game, though that goes beyond the scope of this guide. Getting a couple sets of each can’t hurt if you want to experiment later given that they are event-locked parts.
The two Exodia arcanes have niche uses including one which is real good at killing you by accident. I’m sure they have their fans, but just know these aren’t “required” by any stretch.
The Sacrifice companion mod can be useful, though a better Primed version exists.
If you sold your Ether Daggers before mastering them, these are an alternative to Sephalon Simaris’ extortionist pricing. Otherwise, they and the Snipetron are mediocre mastery fodder weapons and I’m sure their one fan will scold me in the comments for calling them that.
While you can theoretically use standing on rewards like Cetus Wisp, Radian Sentirum, and Heart Nyth (which are annoying resources to gather), I’d argue the Forma farm is more valuable.
-Tell Me More About Armor Stripping-
One way to deal with Hemocyte’s tankiness is to strip its armor after it comes out of the boil and before it opens its heads. It also changes it damage resistances and vulnerabilities. This is by no means required. Here are a few simple (but not all) armor-stripping methods:
+ An Oberon at 169% Strength can combo his 2 and 4.
+ Several alt fire shots from the Sarpa with the Shattering Impact mod equipped.
+ Banshee‘s 1 with 143% Strength and the Sonic Fracture mod.
+ Ash‘s 1 with 143% Strength and the Seeking Shurikens mod.
+Nyx‘s 2 with 125% Strength, but this may be tricky to aim for the inexperienced.
+Mag mindlessly spamming her 3 and 4. (There’s a math involved that I’m too dumb to do.)
Many, many more options can be found at the Warframe wiki. Some of them are a bit more tricky to pull off or require less than ideal builds to accomplish.
-What Type of Damage Should I Mod For?-
This depends on whether you’re stripping armor or not.
Radiation is the best if you know for sure you aren’t stripping its armor, but it becomes a huge liability if you or a teammate does, whereas Corossive is best when the armor is stripped and neutral if it isn’t. Blast meanwhile can actually outperform Corrosive in certain circumstances when the armor is stripped, but is garbage tier if the armor isn’t. For this reason, Corrosive is the safest option.
For more info, feel free to do a deep dive on the Infested Sinew “health” type and its storied history.
-What Info Is Out of Date?-
The big one comes from older articles talking about Ember’s 3 one-shotting the heads. That has since been patched (and Ember reworked anyway).
-What New Changes Are Expected?-
Nothing has been confirmed, but just know that Plague Star has been buffed in the past, so keep an eye on the forum for any new developments. DE have historically been squeamish about bringing back this event since its so reward heavy, and I fully expect them to try to make it harder to slow down the grind. It wouldn’t shock me if some of the newer Deimos enemies were cycled into this thing and/or the Hemocyte tweaked to negate previous tactics. I also have no doubt the community will find ways to incorporate new frames and weapons to better cheese the fight. Y’all are a bunch of freaks.