Magic

The term "magic" is really a layperson's word that has infected the vocabulary of arcane science. Thetic and phrenic magic are entirely different from each other. Shamanic and catabolic are related to each other, but totally unrelated to the others. To analogize: shamanic magic may be thought of as simple tools and mechanisms. Catabolic magic is a great machine built of the same stuff as shamanic magic. Thetic magic is an ally who acts at your request. Phrenic magic is sculpted clay, always being reshaped.
-Ethrenal

There were 4 main types of magic practiced on Abrecis: shamanic, thetic, phrenic, and catabolic. Shamanic and catabolic magic were really the same type, but it was considered shamanic if there wasn't a deleterious amounts of miasma produced.

Shamanic

Shamanic magic was originally practiced by the Ashenal, but after Caer's mistake many newly-differentiated anthropoids practiced it as well. This magic generally operated at a very small scale and/or very slowly. Casting spells to illuminate an area or amplify one's voice were common, as were ones to make crops hardier and more bountiful. These spells did cost life energy and produced miasma, but the amount was negligible. Shamanic spells operated in a manner conceptually similar to machines. Learning the spell meant learning how to "construct" this machine via certain utterances, rituals, motions, or substances that configured the underlying fabric of the universe. Casting the spell constructed the machine, then it to perform an action. A small amount of miasma was a waste product of this process.

Thetic

Thetic magic was magic based on devotion. Most commonly, followers of a deity would be granted the ability to cast thetic magic in exchange for carrying out the deity's will. This magic was powered by a specific external being, and thus did not draw surrounding life energy or produce miasma. In contrast to shamanic magic, thetic magic was akin to sending out a request then receiving what was requested.

Phrenic

Phrenic magic was developed by Ethrenal during the prolific era. Rather than machines or requests, phrenic magic operated via powerful cognition and will accumulating and shaping the energies of the universe. Phrenic magic did not produce miasma, but the mental strain could cause harmful side effects for the caster, particularly caster's psychosis.

Catabolic

Catabolic magic worked on the same principles as shamanic magic, but on a large enough scale that the amount of miasma produced was harmful. No mortal ever had the inherent ability to cast catabolic magic. Rather, shamanic spells could be cast for the express purpose of accumulating more energy than normally possible in the casting of a shamanic spell, bootstrapping a follow-up catabolic spell. As such, the casting of catabolic spells was always technically the casting of 2 separate spells, but the shamanic part would be optimized on a per-spell basis in order to draw as little energy as possible, and the 2 parts were always taught as a single spell.

Casting a single minor catabolic spell might not have any effect, but repeat castings would cause the caster and others in the vicinity to begin experiencing miasma sickness. Casting larger catabolic spells could range from immediately damaging to cataclysmic. Caer's mistake was the first instance of catabolic magic, but due to its failure to do what the caster wanted or even keep the caster alive, Ethrenal was usually the one credited with the invention of catabolic magic.

The arcane arm's race during the first hematic war caused widespread environmental destruction, and by the end of the second hematic war the effects of catabolic magic had pushed the whole planet solidly into a xerothermic state.