Ok seriously, where is the Vault?

[warframe.wikia.com]

Once you're in the mission you will have to search EVERY nook and cranny until you find the vault, or more accurately the smaller doors that connect rooms. The vault will never spawn at one of the larger doors that you may see or the narrower doors that connect the vault to a loot room or an elevator. If you reach the end and still haven't found it that means you missed it, so go back and find it! The Vault will look like this: When you get close to the lock portion, it will tell you which key it needs to be opened. If it isn't yours, mark the vault and call out which key it does need so they can open up the vault. The blue outline shown also corresponds with the key it needs to be unlocked with! This is a view of an opened vault from the outside. DO NOT FORGET TO GRAB THE ARTIFACT. Seriously. You don't get a corrupted mod without it. Anybody can grab the artifact, so don't worry if a teammate grabs it before you do. The player who picks up the artifact will have a rippling, glowing sheen over them as seen in this picture. The artifact will also give a random effect corresponding with the keys. Double Hobbled effect is the best for doing epic slowmo \o/ The "reward" for my run. It's a random chance for each mod and as far as I've been able to figure out the vault location or key has no effect on which mod is awarded.Side note:If you find and open the vault before you eliminate all of the enemies, the remaining ones will spawn as Orokin Void enemies.