The majority of the universe is made of stuff that appears to only interact gravitationally with 'normal' matter. This dark substance comes in two forms: dark matter and dark energy. Advanced technologies - indistinguishable from magic - can convert dark substance into normal matter and energy, and can manipulate normal matter and energy.
Shadow Magic is the ultimate CAD and 3D printer technology: effects can be imagined, designed, and manifested in moments. Sophants with access to this power have the ability to cast spells, causing apparently magical effects by accessing machines made entirely of dark substance. Shadow Magic can be used by Wizards, Sorcerers, and Adepts.
Dark Powers are apparently magical effects that are fuelled by the MRO through an unknown process. Unlike Shadow Magic, there is no theory of how it works. Sophants who use the dark power are Adepts, though some Adepts are known to use Shadow Magic instead.