Diedne the Founder
One of the original twelve founders of the Order of Hermes. She came from a non-Latin druidic tradition. Her collaboration with Bonisagus led to the ability to cast spontaneous spells in Hermetic magic.
It's worth noting that Diedne derived her tradition of magic from druidic practices, and worked with Bonisagus to integrate her magical knowledge into Hermetic theory. It's also worth noting that Diedne's druidic magical tradition was in many ways the opposite to the Cult of Mercury tradition, and standard that Bonisagus and the other Founders created from the Roman Mercurian cult practices. The druidic tradition was a flexible, spontaneous magic without prescribed magical spells (which can be seen in the current Diedne Magic virtue, which excels in spontaneous magic).
Her style of spontaneous magic evidently drew on the physical endurance and stamina of the Magi as a kind of sacrifice, which was carried over into [Hermetic magic] as a price for the use of flexible magic. This method is noted as an overreaching one's magical talents The Gift, as many spells can fail and drain your physical endurance to still function.
Her house was later expelled from the order and likely, but not certainly, destroyed in the Schism War.