It always struck me that Harmony, Purity and Supremacy played more similarly than differently for such wildly divergent alliances. So I put in some thought into how I would make them more different. Here is what I came up with. Harmony Harmony gains quests from the aliens, often involving conflict with other players who've offended the aliens. Completing these quests would reduce the aliens hostility to you, and if you got their hostility into negatives you can gain control of alien nests and units within your territory. Purity When you advance in Purity you gain the ability to terraform automatically. Earth terrain spreads outwards from your cities. Aliens hate this, but alien nests cannot spawn on Earth terrain and have reduced speed and combat strength while on Earth terrain. Supremacy Supremacy can make their cities mobile whether they're on land or water. When they upset the aliens they move away to somewhere where the aliens are less hostile.