As shown Erf-b2-p4, it appears that Dittomancy amplifies bonuses and duplicates units.
- Doubling leadership, special bonuses, and duplicating surviving units.
One in the service of Jetstone, as yet unnamed.
Given the name and the alignment (Stuff, numbers) of the class, dittomancy probably involves multiplying or copying stuff.
Real World References
"Ditto" is a term that has many iterations, all of which involve duplication, repetition, or copying.
The original Tuscan word (cir 1625) meant "in the stated month or year" and was used in place of repeating the same date. By 1678 it was in use in English to mean "same as above," from which we get the "ditto mark" (or "), placed under a word or phrase it is used to repeat.
The Ditto corporation made simple printing devices called spirit duplicators (because they used alcohol), or "Ditto machines" which produced "ditto sheets," or copies.
Ditto was used famously in the film Ghost to mean, roughly, "I feel the same way."
Multiple fictional characters that involve copying or twins, etc. are named ditto.
Jetstones's Dittomancer carries a staff that bears a © (copyright) symbol to support the fact that he has the right to copy.