There are five race-specific uber transformations, which are all acquired by developing Xenobiotics.
- Cavernous transformation (Klackon)
- Grassland transformation (Mrrshan)
- Inferno transformation (Silicoids)
- Tropical transformation (Sakkra)
- Ocean transformation (Trilarian)
Strategy
Cavernous, grassland, and tropical uber planets are significantly better than terran-class planets and nearly as good as Gaia planets, but are accessible much earlier and through fewer terraforming steps. Ocean planets are comparatively a lesser improvement, as they are slightly worse than terran planets and can in fact be further terraformed. Since Silicoids do not need food, inferno planets are for them even better than a Gaia planet, allowing full use of the planet for production but with a higher biome tolerance to pollution.
However, while all non-volcanic natural worlds can be eventually upgraded to Gaia by repeated terraformations until they reach the terran class, not all worlds can be turned into a given type of uber planet: if a barren world becomes a desert world after terraformation, it can become a cavernous or a grassland world, but not a tropical or ocean world; inversely, if it becomes a tundra world instead, it can become a tropical or ocean world but not cavernous or grassland.
As uber planets aren't as good as Gaia planets for most, once a planet has been converted to an uber planet, it can be reverted to its former state by allowing pollution to reach maximum and sitting there for six turns until the biome downgrades to its previous biome. You will then have the option to terraform up to gaia or uber terraform again
Modding
Custom uber transformations are relatively easy. The function used to determine if a colony project counts as a terraformation, Backend.Settlements.ColonyProject.IsTerraformationProject(), looks for whether the colony project's class name is "colonyproject_terraforming" or "colonyproject_gaia_transformation", or whether it starts with "colonyproject_uber_". For example, a mod-added custom colonyproject_uber_ecumenopolis would work just like the game's standard uber planet transformations.