What factions are available in the game? How are extra factions unlocked?

You can play as the following factions in Total War: ROME REMASTERED’s three campaigns:

Base Game
Julii	Brutii	Scipii
Macedon	Egypt	The Seleucid Empire
Carthage	Parthia	Pontus
Gaul	Germania	Britannia
Armenia	Dacia	The Greek Cities
Numidia	Scythia	Spain
Thrace

Barbarian Invasion
Western Roman Empire	Eastern Roman Empire	Huns
Goths	Sarmatians	Vandals
Franks	Saxons	Celts
Sassanids	Roxolani	Ostrogoths
Romano-British	Slavs	Burgundii
Berbers	Alemanni	Lombardi

Alexander
Alexander the Great’s Macedon

To start only the three Roman factions are available in the Imperial Campaign – the Julii, Brutii and Scipii. When you defeat another faction, it is unlocked as playable in future campaigns.

After successful completion of an Imperial Campaign all factions will be unlocked.

To unlock all factions immediately, select Unlock All Base Game Factions from the Advanced tab of the Pre-Game Options window.