There's a fair bit of wriggle room in the term "history-based", but the additions to free-to-play MMORTS Terra Militaris may just have popped some sort of reality seam, flooding the pre-industrial world with guns and monstrous house-sized pets. All for the better, I say: the new Firearms expansion not only brings a satisfactory quota of splodes, it also overhauls a good deal of the game.
There's a new pet system, a new crafting system, tweaked building and research features, a higher level cap and quicker era progression. Players can now challenge each other in a new arena ranking system, and compete in ten versus ten battles - although only if they've hit level 50. Needless to say there are loads of new units, too, poised to unleash their might this autumn.