Getting the Underdome achievements, easy and solo!

Let's cut to the chase. You want the larger challenge achievements from Mad Moxxi's Underdome Riot, but who wants to spend hours doing such a chore? Here's how you get them, easily and with a single copy of the game.

Part 1: Getting ready

Let us be clear from the beginning: you WILL need to do each challenge completely. But thanks to the technique described below they will be effortless to beat. Just listen to your favorite podcast while tearing through hordes of inoffensive foes!

Here is what you will need to perform this trick:

• A single copy of Borderlands 1
  
• 2 computers running Windows. The second computer doesn't need to be powerful. As long as it can run Borderlands on the lowest settings and connect to the internet, you will be okay.
  
• A save file with a reasonably high-leveled character so you require minimal effort to tear through the numerous waves of buffed-up level 12 enemies you're going to face.

You might wonder why this guide is needed and why so many steps are needed to get to our end result, and the reason is rather simple: the "LAN Game" feature of Borderlands, which is needed for this to work with a single copy of the game, is broken ever since GameSpy was retired, and the following trick will bypass the issue and allow us to play on LAN.

NOTE: This guide making use of the LAN feature of the original Borderlands 1 means it is not applicable to Borderlands: Enhanced Edition, from which it is absent. Therefore for that version you will not be able to perform this trick on your own and will need a friend to mimic the second computer. However if you own both editions of Borderlands 1, you can "transfer" your achievements to the new release as will be explained in the Bonus part at the end.

Part 2: Setting up

First and foremost, connect both computers to the same network. One can be on Wi-Fi while the second uses Ethernet, that is not a problem. As long as they both use the same local network, you will be okay.

Note: It is possible to do it across two different networks if you really cannot avoid this, but you will need to perform something called "port-forwarding" to be able to use the "LAN Game" feature. How to do this is beyond the scope of this guide, but you will find thousands of guides online that explain the necessary steps in great detail.

Install Borderlands on both computers. We will refer to the two computers as the Guest and the Host. Here is how you need to setup each of them:

Host

The host will be your weakest computer. Again, as long as it can run Borderlands on minimal settings, you have what you need. You will not be playing on that computer.

We need to get some information from this computer, namely its local IP address. This can easily be done in the following way:

• Open a Command Prompt by typing "cmd" in the Windows search bar and clicking on "Command Prompt"
  
• In the Command Prompt that opened, type "ipconfig"
  
• Find the address next to "IPv4 Address"

Your local IP address should have the format "192.168.000.XXX". Write that address down for now and proceed to setting up the Guest PC.

Note: If you tinker with this PC by turning it off and on or disconnecting from the network, your local IP address might change and you will need to redo these steps to obtain the new one.

Guest

This is the computer you will be playing on. The Guest needs a bit more setup than the Host. Navigate to the game's executable. Here's how you get there from your Steam library:

• Right click the game in the list OR click the "gear" icon on the right side of the game's page
  
• Go to "Manage"
  
• Click "Add Desktop shortcut"
  
• This creates a shortcut named "Borderlands" on your Desktop
  
• Right click the shortcut
  
• Go to "Properties"
  
• Under "Target", go to the end of the text, put a space and add the IP address you wrote down before

The "Target" field should now look something like this:

<Path to your Steam install>\steamapps\common\Borderlands\Binaries\Borderlands.exe 192.168.000.XXX

Why we are doing this will become clear very soon. Hit "Apply" then "OK". You are now ready to play.

Part 3: Grinding the achievements

It's time to play! The way this is gonna work is the following: we will create a LAN game on the Host PC and join it with the Guest PC, all with the same copy of the game, and take advantage of the fact that enemies follow the level of the Host character to grind these achievements easily.

Here are the steps to connect both computers:

Host

First and foremost, put Steam in offline mode. This can be done by clicking "Steam" at the top left of the window, then clicking "Go Offline". This is important as Steam will not let you run the game twice on two computers while Steam is online on both (it will force the streaming functionality instead, which we do not want). Here are the final steps on this machine after this is done:

• Launch the game
  
• In the main menu, go to "LAN Game"
  
• Select a character with a level 12 or below. This is because the enemies in this DLC start at level 12 and we want them to be as weak as possible.
  
• Go to the Guest PC

Guest

The final steps are really simple. Just double-click the shortcut we created; this will launch the game and immediately join the LAN session hosted on the other computer, simple as that! All that is left to do is start the game on the Host PC and grind some achievements!

Just let the sub-level 12 character die over and over again. You can even use them as a bait for the horde waves. If you are high-level, you will be virtually invincible, although some very specific attacks CAN down even a level 69 character. But worry not! If you die, you will simply have to restart whatever round you were in and will not go back to the beginning, so if that ever happens, DO NOT GO BACK TO THE HOLODOME.

Happy grinding!

Huge props to Nausicaä who wrote a life-saving guide about the neat trick that fixes LAN play post-GameSpy!

Bonus: "Porting" the achievements to Borderlands: Enhanced Edition

Wanna get 4 extra free achievements? You're in luck! All mission-related achievements are automatically unlocked in Enhanced Edition when you load a transferred save file that has these missions completed. Meaning that after completing this guide, you can simply import your save in Enhanced Edition and start the game, which will immediately unlock the 4 achievements on that game as well, without needing to go through the chore all over again.

Note: Our missions aren't technically in the mission list, but their completion is still recorded on your save file in the background.

[Nagra]

I mistakenly published his for Borderlands EE instead of Bordelands. Published again here : https://steamcommunity.com/sharedfiles/filedetails/?id=2905512475