Southern magic

Southern magic was a term used to describe spells written in a different magical language. While many spells common in the rest of Faerûn were also employed by mages in the south using this language, they also created a number of unique ones unknown outside their ranks. The term also applied to certain spellcasting techniques that blurred the line between arcane and divine.

Origins
As the named implied, southern magic originated in south Faerûn, specifically Halruaa, Mulhorand, Unther, and parts of Chessenta. Wizards who were not native to those lands could not read spells or scrolls written in the southern magic language, even through the use of a read magic spell. The distinctive script was originally developed by priest-mages of Thoth to protect their secrets after the secession of the former Mulhorandi province of Thay. Therefore, it became also known as Thoth mage-script.

Usage
A Mulan human who mastered southern magic, known as a "southern magician", learned to weave magic in an unusual manner, blurring the distinctions between the arcane and the divine. Although the source of a spell and its preparation remained the same, a southern magician could cast an arcane spell as divine or a divine spell as arcane, allowing them to access different benefits or to circumvent the restrictions that encumbrance or armor typically placed on arcane spellcasting. Such spells were confusing to those not versed in these techniques, and they struggled to identify, counter, or dispel them.

Rumors and Legends
In the mid-1360s DR, the brilliant wizard Random Riellor successfully created a spell that allowed non-Halruaans to decipher a spell written in southern magic. This spell was called read southern magic. Random only shared this spell with those he believed would help further his research.

There were also rumors that there existed practicioners of path magic in the magic tradition of these old empires, following a Road of Southern Magic.