The Source

• Training the Gift of Magic
• Mass worship or veneration, or on the flipside, fear or dread, can result in an individual gaining magical abilities; this effect tends to be "aspected" (positive abilities for veneration, negative/destructive abilities for dread). Generally requires a lot of people, such that the greatest of kings might be able to pull off a minor feat or two in their lives, but nobles of long-renowned bloodlines might exhibit effects like actual blue blood.
• Overall Mana Level: Average. Pockets of High or Low Mana exist. Living near high-magic areas a bit like living near a kinda-leaky nuclear facility
• Mana-based "weather" occurs, behaves like physical weather, and is predictable by trained wizards; can raise or lower the local mana level. "Storms" are also possible.