Nehahra was also a 4 hour movie called The Seal of Nehahra that acted as a companion to the main quake single player and a lead-in to the Nehahra game. I take 5 mins at the start of my video to summarize it but the rest of the video talks about the mod itself.
I highly recommend playing it, it beats out the official mission packs by far and has the added bonus of being fully playable in Co-Op.
Taken from my video description (Links are subject to change or death):
****How to get and Install Nehahra Quake****
1 - Get Quake (the first one, NOT Quake 2, 3, or 4): http://store.steampowered.com/app/2310/
2 - Get the latest version of Darkplaces: http://icculus.org/twilight/darkplaces/
3 - Get Nehahra Full - http://www.moddb.com/mods/nehahra/downloads/nehahra-full
4 - Get The Seal of Nehahra - http://www.moddb.com/mods/nehahra/downloads/seal-of-nehahra
1 - Install Quake
2 - Install Darkplaces into the Quake Folder
3 - Install Nehahra Full into the Quake Folder.
4 - Install The Seal of Nehahra into the Quake Folder. (YES Overwrite any files when asked.)
Inside your Quake Folder there should now be several new program files as well as a Nehahra folder.
5 - Open up notepad.
6 - Paste in the following line:
darkplaces.exe -nehahra -game nehahra
7- Go to "Save As", in the Save as File type box, change it from Text Documents to All Files.
8 - name the file nehquake.bat and save it into the quake folder
#How to Play
1 - Go to your Quake Folder, double click on Nehquake.bat
This will run the Darkplaces Engine in Nehahra Mode (special engine features), using the Nehahra game (instead of ID1 which is standard quake).
2 - Go to Single Player, New Game
3 - You are in game! Choose your difficulty level, choose wisely as EASY is like normal Quake's HARD, and anything harder is insane by normal gamer standards.
4 - Once you start the game a 15 min introduction cutscene will play, then you will gain control of your character.
#How to Play Co-Op (aka ONLINE or LAN WITH FRIENDS)
1 - Make sure all of your friends have installed this properly.
2 - Go to your Quake Folder, double click on Nehquake.bat
3 - Go to Multiplayer, New Game, Set your PORT (More below on that).
4 - Change Game Type from Deathmatch to Cooperative
(NOTE: Nehahra does NOT support deathmatch, so if you try to make a Deathmatch Nehahra server without massive tweaks to the levels, things will get SCREWY.)
5 - Teamplay On
(NOTE: Teams are defined by the pants color, all players of the same pants color will not be able to friendly fire each other. You can change pants color in Player Setup under Multiplayer)
6 - Skill Anything you want but for Co-Op I EXTREMELY recommend NIGHTMARE.
7 - Frag Limit and Time Limit should both be NONE.
8 - Public Server on if you want random people to see it on the server list, otherwise off.
9 - Server maxrate (Don't mess with this unless you know what it means) 1000000 is default.
10 - Server Name, whatever you want.
11 - IMPORTANT: SKIP THE WELCOME LEVEL FOR CO-OP, start on
The Fall of Forge
Forge City1: Skipgates
12 - Have any friends run the game and then go to Multiplayer, Join Game, Make sure the PORT is the same as yours, and connect to your IP address.
Q: Friends can't connect to my sever!
A: Is your router configured to have the port your server is on open?
Q: I don't have access to my router to fix it! What do I do?
A: If you are one of these sad individuals, then you and all your friends will have to resort to using a program like Hamachi in order to host and join servers. I will not be providing information on how to do this.