These are young Amunian worlds, having an atmosphere of gaseous ammonia, methane, and small amounts of water droplets. As the planet ages and cools, these components will be broken down into nitrogen, carbon monoxide, and a hydrocarbon 'tar' that will rain down on the surface.
Ammonia oceans will condense on the surface during this period, and the earliest forms of life will develop. These organisms will be acidophilic due to the presence of dissolved water, but they will begin converting the present oxygen into sulphur dioxide as a part of their metabolic processes.
Such worlds go through several stages as they evolve towards being MesoAmunian.
Typical Habitability: IV (Cold, unbreathable)
Typically have low proportion of liquid surface, initially less than 10%, with a thick atmosphere of mostly ammonia and methane, with some small proportion of water droplets. As the planet ages and cools, the atmosphere will break down into nitrogen and carbon monoxide, and ammonia oceans will grow to nearer 30% of the surface.
The land surface may be a mix of water-rock and carbon compounds.
Typical Habitability: V (Extreme cold, unbreathable)
Ammonia oceans may cover over 50% of the surface, and life may begin to form in the oceans.