Nekros and Zoì
Two forms of Theurgy that overlap somewhat but are discernable by the trained eye. A quick look at their history can help understand them.
Nekros originates in the Roman Empire in 21 BC. Its purpose was to develop a way to stop the civil wars and keep the civilians at bay, but it went horribly wrong and many Theurges died attempting to use it. Discovering the ability to effect peoples' life force allowed them to take control of such a large area of the world.
Zoì originated in Greece in about 200 years prior to Nekros, but did not become heavily used until the discovery of Nekros. Greek Theurges used their power of protection and healing in competition with the Necrotheurges.
The competition lead to the Battle of Life and Death, held on Othonol which ended roughly 500 of the most powerful Theurges at the time.
After the battle, the remaining Theurges learned from each other, which is why some Zoì has Latin names and some Nekros has Greek names. It is also the reason that most form of healing are classified as Nekros instead of Zoì; They were invented in Rome and manipulated life force rather than the Aether in order to heal.