Adding a new civ to Forgotten (non HD) goes a little something like this
Go to your age of empires 2/games folder. Open age2_x2.xml with a word editor (notepad++)
copy the last line, paste and rename/edit the details of your new civ.
Then download resource hacker, open the language.dll file,
Find the other civilization names by using cntrl+f and add a new line with the new number in chronological order for your civ.
There are 2 spots, line 1261 (?) for the civ name, and one other one with the civ descriptions (when u click the folder in the pregame lobby)
Dont forget to compile and save.
Ive managed to add 4 civs this way, 3 with descriptions, after that u run out of room it appears in the language.dll I am looking for help to find a way to add more.
This link should help
https://www.youtube.com/watch?v=gIL0qk2f810[This message has been edited by Havie (edited 05-01-2015 @ 12:28 PM).]