Roman Empire: Expands from Hispania in the west to India in the east and from the Baltic Sea in the north to the Congo in the south. The single largest Empire on the face of the Earth, even without help from their gods, Rome would be well equipped to take on any threat. In battle they use a mix of traditional soldiers as well as a number of mechs crafted by Vulcan. Mechs come in various varieties, modeled after different deities and prominent figures from history. The most powerful mech: Romulus is piloted by the emperor himiself, and while it's usually stationed in Rome, it has been moved to take part in battles elsewhere (generally when the emperor has grown impatient with the progress of his commanders).
Britons: A small band of relatively rag tag barbarians. They managed to fight off the Roman invasion of the British Isles and make a successful counter attack, taking the northern part of Gaul. Using captured mechs and crudely built replicas, the Britons are a thorn in the side of the Empire.
China: Rome's most powerful opponent, China is capable of fielding scores of soldiers, the majority of which are terracotta golems. In addition to crushing opponents under the weight of numbers, the Chinese make use of a number of technological advances, the most notable of which being the use of rockets. Similar to the Roman Romulus, the Chinese have a similar war machine: The Jade Dragon.
Mongols: Swift and deadly, they outfit soldiers in fast biological suits. They're currently pushing down into China from the north as well as into Roman controlled Middle East via the Caucuses.