Orokin Vaults are an old, old part of Warframe. They’re the only place to get Corrupted Mods, which have both a negative and a positive. However, these vaults aren’t just old, they’re archaic as well. And it was only with the appearance of Deimos that they became far more accessible. What’s more important though is that these Orokin Vaults are easier to solo than ever.
You don’t actually need to solo them though.
I should probably start by pointing out that Deimos has normal matchmaking. Back when the Orokin Derelect was the home to Lephantis, you needed keys to access every mission. This meant that you couldn’t just grab a key and start the mission and be matched into a squad. You either needed to make a squad in advance, or go in on your own. Even further back in the past, you 100% needed a squad. Because the ability to equip multiple Dragon Keys at once is a more recent change.
That being said, if you’re going with a group, you can’t guarantee what keys everyone else is carrying. Or that people will even have keys at all. So being able to carry all 4 keys on your own is a useful skill.
Almost any frame can get away with using the Hobbled Dragon Key, which reduces speed. The Extinguished Key can be worked around by bringing really strong weapons to what are otherwise level 25 and below missions. Decaying and Bleeding Keys are a little bit trickier. Although you can just slap a Decaying Key on a Shield-less frame like Nidus or Inaros, Bleeding Keys take away 90% of your health.
None of this is a problem for Rhino. You can bullet jump and use Rhino Charge to get rid of the Hobbled downside, and Roar gets rid of the Extinguished Key’s damage reduction. Meanwhile Iron Skin completely negates the downsides of the Decaying and Bleeding keys. So you can put all four keys on Rhino and easily make your way through a mission on Deimos.
You don’t even need a particularly strong build.
A bare basic Rhino with a basic Intensify and enough energy to be able to cast Iron Skin at the start of the mission is generally enough. Flow and Streamline are useful, since Parasitic Eximi are somewhat common. But you don’t really need much else. Unless you’re attempting to open vaults on the Steel Path. But frankly, that’s not worth the hassle.
You can use other frames too. Wukong’s Celestial Twin ignores most downsides and deals with enemies no problem. Limbo can also ignore most damage. However, you do need to leave the Rift to open the Orokin Vault itself and pick up the artifact, which does leave you vulnerable. Rhino though is cheap and easy to get, and pretty much everyone has one.
What mission though?
Really, the only choices are Exterminate or Capture. Exterminate is a longer mission but tends to have less rooms. Capture missions are longer, but you can freely wonder around once you’ve completed the objective. The enemies are mostly infested but there are also often Grineer or Corpus running around as well. The more important thing is that Capture and Exterminate are lower level missions, meaning the enemies die more quickly, and you don’t need to worry about the Extinguished Key’s damage reduction.
Once you’re in the mission, there’s not really much to do apart from do the objective and then look for the vault. I do recommend though taking the time to check rooms in the spawn area. It’s easier to check first rather than having to backtrack across the entire map.
All this, for some corrupted mods.
Unfortunately, most of the time, you won’t get much from doing Orokin Vaults. Orokin Ciphers are used only in the Hidden Messages quest for Mirage. And the Corrupted Mods are very hit and miss. The only genuinely useful ones are the Warframe mods, and maybe a handful of the primary ones – notably Heavy Caliber and Vicious Spread. And these only count because their negatives are heavily outweighed by their positives.
Still, you can sell these mods for a little bit of platinum. And being able to solo these missions makes the Nightwave task so, so much quicker…