Lamia aren't supposed to be playable, they weren't disabled in the scenarios for some reasons, but their won't be any update concerning them for a -long- time.
If you wan't to play this game, I recommend playing the factions enabled as of now, the complete list will be accessible with the Play Now button.
The (uncomplete ?) list : empire, bretonnians, the 3 elves nations, chaos nations...
And I don't know what you mean with 'not that long', you've started coding stuff ?