Primordial world

Size: 10000 km - 15000 km
Atmosphere composition: Nitrogen, Carbon dioxide

A very young world. Atmosphere poisonous (usually reducing, being composed primally of nitrogen and carbon dioxide with variable amounts of water vapor, ammonia, methane, carbon monoxide and hydrogen sulfide).

Usually have a partially molten surface because they have been recently formed. Geologically unstable. Lots of volcanos and magma seas.

Sometimes referred to as the "Geo-Plastic" type.