Miasma

A miasma is an oppressive or unpleasant atmosphere. The term commonly refers to the dark side of the Chaos Force, which draws from the sins and negative emotions of living beings.

Users
As with the positive side of the Chaos Force, the miasma permeates all existence, but is concentrated within the seven Chaos Emeralds (and to a different extent the Master Emerald).

By channeling the Chaos Emeralds through the Altar of the Emeralds, the water spirit Chaos is able to absorb the miasma and transform into his Perfect state. Similarly, the earth spirit Dark Gaia absorbs miasma through the Gaia Temples to attain its own Perfect state, but this process is much slower and can take thousands of years.

Shadow the Hedgehog has a unique relationship with the miasma and the rest of the Chaos Force, being able to absorb its energy directly using his Chaos organ and harness its power for abilities such as the Chaos Blast.