In true Warframe style, the Plains of Eidolon are as confusing as anything else in Warframe. Nothing is explained. You just have to guess. Well, not any more. Here’s a crappy, brief explanation of, well, the basics. Since no one tells you.
Getting to the Plains
You have to go to Cetus to go to the Plains for the first time. You’ll land near the big Orokin tower and have to walk through the market towards a massive Orokin door. The door will open and once you step through and go a certain distance, the door shuts, you get a loading icon and eventually you’ll draw your weapon and be able to roam around. To get back out, you go back through the doors. The loading icon will appear, then you’ll put your weapons away and a mission success screen will appear (which you can hit ESC to get out of).
Ostron is basically a massive syndicate. Everything costs ‘standing’ or reputation, and Ostron has ranks, the same way syndicates do. The difference is that there’s no negatives from Bounties. So there’s no way to piss them all off. You can earn standing by doing bounties, doing random missions on the plains and by trading gems and fish to their respective NPCs. There is a limit to how much standing you can do in a day, but this resets every 24 hours.
Bounties aren’t obvious either. It’s actually a set of 3 to 5 mini missions that you need to complete. You get around 100 standing for each one, but
to get the actual reward, you need to successfully complete all 3-5 missions you now get a reward for each stage but the best loot comes from stages 4 and 5. You start off with one mission that activates as you get onto the Plains. Once you’ve done that, after a few moments, Lotus will point you towards a new objective. And so on and so forth. Luckily, standing and rewards are saved the moment you finish the bounty, so you don’t need to worry about returning to Cetus.
Fishing is relatively simple. Buy yourself a fishing spear from whatshername near the entrance to the market area of Cetus. It costs 500 Ostron standing, so you’ll need to do a few bounties first. Equip the spear in your Gear slot. When near water, pull out the spear. If you hear splashing, there are fish nearby and you’ll be able to see them in the water. Simply throw your spear at the fish and it will reel in automatically. You’ll get a little cutscene of you and your fish if you succeed. Fish can be taken back to the fishing stall and either traded for Ostron standing or turned into crafting components for other things. You can buy dye to make fish easier to see, and you can buy baits to spawn rarer fish. These need to be thrown in ‘hotspots’, white splashes in the water, to work.
Mining is also pretty simple. Once again, you need 500 standing to buy the mining tool from the mining stall (which is round the corner from the fishing lady). When you’re out on the plains, you can equip the mining tool and your HUD will have a ‘mining overlay’. A small gem icon appears on the side when you’re near somewhere that can be mined. You’ll see blue or red marks on rocks, and these can be mined. Zoom in to the rocks with the tool and you’ll see a pattern that needs to be traced out with the mining laser. Start tracing by holding left click. As you do so, the pattern will fade so you’ll need to try and memorize it. The better the job you do, the more ore you get. You generally need to refine the stuff, and you can buy refining blueprints from the mining guy.
Archwing in the Plains
This is another gear item, and can be crafted in the Foundry on your ship. It needs a ton of items from the Plains though – yellow stuff from Grineer camps, Iradite from the random little red ‘poops’ found sticking out of the ground and 150 fish oil, obtained by cutting fish down via the fishmonger. As it’s a gear item, it needs to be thrown into the Gear slot before it can be used.
Grab those little floating fuckers before they float off into the air and escape.
The Quills are the secret group behind the Ostron, and they have all the stuff you need for Space Kid stuff. The entrance to the secret area is behind the bounty-giver, or via a path to the right just as you enter the Cetus marketplace. But you need to complete Sara’s Vigil before you can get in. Once you’ve done that, active Space Kid mode when near the door and it’ll open up. You can increase your standing with them by killing Eidolons and Sentients.
The little Sentients floating around at night have two forms – one that can be damaged by any means and one that can only really be damaged by using Space Kid mode and Void-beaming them to death. You need to have finished the War Within to kill them.
I don’t really know, to be honest. Basically use space kids to destroy the Eidolon’s shields then shoot its limbs. It teleports away, you find it and destroy its shields and shoot its limbs, repeat a few more times, stop it from healing by killing the little floating Sentients and make sure you pick up all the Sentient Cores that drop. You’ll want to use Space Kid a lot. If you don’t have Operator Mode available, stay away from the Eidolons. You can use Eidolon Lures to stop it from teleporting away. A larger guide is available here.
Just keep in mind that there’s no need to rush and get everything done. It all takes time. And a lot of resources and standing are needed. Don’t worry about falling behind and not getting all the awesome loot, it’ll all be waiting for you.
Hopefully this should help a few people out!