Ars Magica RPG: Source: Houses of Hermes: True Lineages

The True Lineages are the backbone of the Order of Hermes. In these four Hermetic Houses, each magus was taught by a magus of the House, and that master-apprentice relationship goes back to the founders. This sourcebook details the four True Lineages, including rules for original research, unique forms of magic, and new Virtues and Flaws.