User is able to create entirely new forms of magic, including crafting/designing their own rules, limitations, maximum potentials, taboos, and everything else necessary for the new form of magic they created, they can even remove the magic they crafted from others if they feel its being misused.
Unlike spell creation however, user has to discover their own spells and possible uses as they cannot simply create new spells on the fly.
Seath the Scaleless (Dark Souls), Grandfather of Sorcery
The Witch of Izaleth (Dark Souls), the Godmother of Pyromancy
By combining the traditions and philosophies of Thelema, Architectural Buddhism and a form of Druidism that does not exist yet, Basil Sage (Grindhouse and Watercolors) has discovered and has since become the father of a new form of Earthly witchcraft.
When Precht (Fairy Tail) tried to revive Mavis after she died he failed countless times before he accidentally managed to create...
..Eternity Magic: Fairy Heart, a completely unique and entirely new form of magic with literally infinite uses.
Irene Belserion (Fairy Tail) is the creator of the Dragon Slayer Magic.
Glyph Magic (Legacy of Kain) is a type of magic created and utilized by the Hylden for a variety of purposes, such as operating machinery, providing light and heat, and to hunt down and kill vampires.
Mammoth Mogul (Archie's Sonic the Hedgehog) is the creator of the Ixis Magicks, a type of magic that centers around elemental manipulation and Chaos Energy.