The Plexus is a new system that has been introduced to Warframe in Update 29.10.0 to replace the old Avionics system in Railjack. All players now have a Plexus, a piece of equipment they are automatically given that comes into all Railjack missions with you. Avionics have become three different types of mods, and you can slot them into the appropriate part of the Plexus.
To access the Plexus, you can visit the Dry Dock, your Orbiter, or the Dry Dock in any Relay. There is a new console in the Orbiter to the left of the main navigation console that will allow you to see your Plexus and Intrinsics menus.
Leveling up the Plexus
The Plexus now places a limit on the maximum number of Railjack mods you can equip, exactly the same as a Warframe does. It is possible to level up the Plexus to increase the overall capacity, however. To do this, all you need to do is play Railjack missions. Because the Plexus is effectively in the mission with you, it will earn Affinity as you play and will be leveled up the same as any other weapon or Warframe in the game.
Upgrading the Plexus
The Plexus can also be upgraded. It will automatically have an Orokin Reactor installed, and you can use Forma to change the polarities of different slots reduce the capacity cost of the installed mods, just like your Warframes and weapons.
To place mods, open the Plexus and you will see the below screen.
It will contain three tabs. Your Integrated Mods that are split between the Aura Mod and Personal Mods, the Tactical Mods, and the Battle Mods. Much like Warframes, your Railjack will have a maximum capacity, and you can place the mods you want as long as it remains below that capacity.
Upgrading Mods is identical to the Warframe Mod system, and all Dirac has been converted into Endo for upgrading purposes. All spent Dirac has been refunded, and all other Dirac will be converted to Endo at a rate of 1 to 1.
Once again, you will only be able to upgrade mods to your maximum capacity, if you upgrade a mod beyond that point you will not be able to use it.
Mods can be earned in Railjack missions, and will often drop from slain enemies and can then be picked up by flying the ship through them, so keep a close eye out for drops.
You bring it with you
The most important part of the Plexus is that it travels with you from mission to mission, so you mod setup is the same across all missions, you are not bound to the setup that other players choose for their Railjacks like you were with the old Avionics system.