Occurrence
This contains occurrence in its most basic sense: occurrence as such.
This realm may seem vaguely defined, but this is an inherent property of the base realm as there are no underlying modalities from which to distinguish it.
The occasions in this lowest realm are known as quantum events.
Equilibria arise spontaneously in accordance with physical law, but this law is statistical not deterministic, and the indeterminacy is not meaningless randomness but leaves physical concrescences free formally to prehend data from dependent realms, so giving rise to the types of physical equilibrium corresponding to cells, organisms, etc.