Mana floats through the air and passes through all living creatures. It is inhaled, exhaled, and cycled through life and death in Costrus. It is both untouchable and yet woven into the very fabric of living things. This source of magic in Costrus condenses in the blood of animals, and the fibres of plants, making the harvesting and harnessing of it possible. Once harvested mana can be used to perform great works of magic.
Collecting mana can be a tricky process and there is no way to know the exact concentration in a living creature before a spell is cast using their blood or fibres from plants. There are records that indicate some species are more efficient at collecting mana within themselves. Indicators that a person has high levels of mana is the ability to wildly cast magic without runes or alchemical processes. Plants high in mana tend to glow, the brighter the glow the more mana a plant usually contains, although some exeptions to this rule exist.
Generally Yildae are seen as possessing the highest percentages of mana in their blood, with even the weakest of their number able to use magic to transform into an animal. Humans are believed to generally have lower concentrations but rarely a person is born with a greater capacity to accumulate mana in their body. Haldae are the real wild card, they may take after either parent and end up with high or low mana concentrations. Not much has been done in the way of testing animal species for their mana concentrations after it was noted that most have less than the average human in the early days of studying magic.
The Wonderful World of Plants
Entire chapters of mages' tomes are dedicated to plants and their individual purposes and mana capacities. Even laymen know that glowing plants contain high levels of mana and can be sold at high prices to mages. However, more specialized knowledge is required to find the more secretive plants that disguise themselves as other species. It is unclear when this defense mechanism began, but there are several records of mana rich plants losing their glow and taking on more mundane appearances, often mimicking other plants. Some mushrooms have developed the ability to glow without mana simply to be carried over long distances to spread their spores.
Harnessing mana can be done in three ways. Wild or innate magic discharges mana without much direction other than the strong desire of the one casting it. For the Yildae this manifests as the abilty to change their shape at will, an innate ability that doesn't cause damage to the user. Wild magic carries many risks to the user, and is usually a last resort for a person with a large capacity for mana. These wild outbursts can cause physical damage that is either immediately visible or over time ravage the body slowly, this is often seen in Haldae or humans who do not know the cost they are paying. Most mages only use wild magic when a situation is utterly hopeless and they have nothing left prepared.
The more common methods among those who know how to use them are runes and alchemy. While many Yildae learn basic runes and alchemical reactions humans lag far behind and their kingdoms safeguard and hoard the information as much as possible from their population. Mages are among those with the most indepth knowledge and skill to use these methods, but keep the information out of the hands of the general public, instead focusing on teaching small numbers of students who show promise.
Of course, there's a little more to it than this...
I haven't even been able to get through all the plants, I think I could study them forever and never know enough.
Strangest thing. A mage came into town last week and started hollering and acting like a madman over my garden! He offered 3 whole gold pieces to dig it up! Crazy or not, 3 gold is 3 gold. I can always plant more flowers.