In the homecity file, look for the line:
line [activetechs]
These are all the cards than you can use in the game.
Now, for instance, take this tag:
[tech dbid =\"2030\"]HCExtensiveFortifications[/tech]
and paste this tag between the tags [cards] [/cards]
Then change the tag [tech into [card and [/tech] into [/card], so it would read:
[card dbid =\"2030\"]HCExtensiveFortifications[/card]
Save the file. When you start a new deathmatch game you will see that you have …. 21 cards out of 20… Funny, isn’t it?
So, any card that is available in the file - you can have it placed in your deck. The only restriction is that you shouldn’t have more than eleven different cards for each of the 4 ages, otherwise the game will crash. Thus, a maximum of 44 cards is possible (which is actually a lot!).