A realmverse is a universe that exists in 3-Dimensional Space. It is believed that our own universe is a realmverse, as humans only perceive three spacial dimensions (and one temporal dimension). Higher dimensions must therefore be rolled up at extremely high energies. Realmverses are the lowest-dimensionality verses that we know have life and intelligence; after all, with only three spacial dimensions (that we're aware of) those things developed on Earth.