Mnemomancy
Mnemomancy (or memory magic) is an arcane tradition focused on the extraction, insertion, and manipulation of memories and knowledge. The school is tightly controlled, maintained and guarded by The Mnemomantic Guild and practitioners are required to be licensed by the same (or are otherwise aggressively pursued by the guild).
Rediscovery
Although it is now ubiquitous in modern Acaelica, the practice of mnemomancy (like most similarly ancient wisdom) was lost for centuries following The Spellplague. It was not until The Ark of the Bygone was located by Dolmin Evengift that the tradition was re-discovered. The historical impact of Evengift's triumph cannot be overstated, as it was directly responsible for the return of arcane magic to Acaelica.
Short of the Spellplague itself, virtually nothing else may be said to have shaped the modern world more completely than mnemomancy.
Societal Transformations
In the centuries following the Spellplague (when arcane magic utterly ceased to function), all schools of magic understandably ceased operation. Sadly, most of the knowledge that remained following the calamity was lost over time (as fewer and fewer could justify its continued practice). Ultimately, magic was believed to be lost forever. However, once magic abilities began to resurface as new sorcerers began to appear, the search for the lost arts began in earnest. While certain spells were able to be recovered via scrolls found in various pre-Spellplague ruins, much of the arcane remained unknown.
However, Evengift's discovery of The Ark of the Bygone uncovered myriad mnemomantic archives. These contained the core tenets of every school of magic, as well as memories of quintessential spells from each. The first class of new wizards in over a thousand years was born of memories collected from these unknown sources. This new class reestablished magic education in earnest, and their efforts would shape Acaelica as it is today: with magic being commonplace just about everywhere on the continent.
Beyond the innumerable ramifications of rediscovering the arcane, the art of mnemomancy itself has also shaped Acaelican society quite directly. For example, the ability to remove a memory from one source before implanting it in another has turned memory into currency. The Society of Mnemomancers -- whose members are often called "brokers" for short -- operates in close conjunction with Kairos to facilitate the secure exchange of information as payment for contracts.
Furthermore, the ubiquity of low forms of mnemomancy has allowed for the retail sale of basic knowledge and education. When The Party arrived in Necine, they were able to purchase something called a "cartog," which they expected to be a simple map. Instead, however, they were offered a small glass vial containing a bizarre swirl of shifting colors. Per instruction of the salesman, Murmus Bigtoe released and inhaled these colors before finding himself suddenly well acquainted with an entire city he had never before visited. In fact, it bore a strong resemblance to magic used by Sinfarena to prepare Murmus and the party to navigate Sunhallow.
More powerful versions of this same magic are in fact able to instill entire skillsets in a breath. One can even become fluent in a language simply by consuming the memory of another who had previously learned it. These types of exchanges (while perhaps not entirely rare) are prohibitively expensive for all but Acaelica's wealthiest individuals.
The ability to remove and alter memory at will of course comes with dark implications as well. Though it is considered extremely taboo (and in many places can be punishable by fates worse than death), there is little doubt that this activity takes place with some frequency in noble courts and political exchanges. Unfortunately, actual evidence of this particular evil can be hard to come by.
Mnemomania
Mnemomania is an uncommon but extremely dangerous affliction that results from consuming either multiple conflicting or individual corroded memories. During mnemomania, an individual's mind is unable to process its contents in a normal way and instead "rejects" its own memories, causing the victim to experience symptoms of madness, fugue, intense pain and even death under rare circumstances.
Although removal of the consumed memories is enough to prevent further damage, effects suffered as a result of mnemomania are often permanent. Although operating through The Mnemomantic Guild guarantees protection against the condition, the guild still maintains a hospital for patients living with its long-term ailments.
