Many creatures in Gaia have magic but there are limits based on species or inherit abilities. Such as a forest nymph. They can make things grow and can to extent control the plants but this magic can't extend to water for example, or fire. Mages are born with innate magic but they are born into a 'sect' of magic, meaning it is much easier to learn from that 'sect' and almost impossible to branch out.
Certain humans can use magic. Usually its genetic but a human that can use magic(called casters) can show up in family that don't have history and families with a history can have a normal human member. These casters, have a different set of rules. For humans, magic has a price. Energy. The casters own life force. Casters are born with something called a core, hidden behind the heart. This core allows casters to convert their own energy into magic. Not all Casters chose,however, chose to go beyond the magic spells or don't chose to learn magic at all. It can kill the caster or burn away their magic permanently, depending on what is trying to be accomplished. This is why young and inexperienced castors must be careful. Magic is like a muscle and must be built up over time. The body must become used to its life force being used this way and must learn to compensate.
There are limits and rules surrounding magic. Magic cannot do everything. It cannot heal every illness, it cannot fix every hurt, it cannot go against nature. For magics such as controlling the weather, unless it is a creature that naturally has that ability, a large coven is needed. Same with large curses that would cause a large change. Somethings, once done cannot be undone.
During a burnout( permanent or temporary) the caster will feel like they are burning alive. In the case of death this sensation will engulf them and their system will shut down as all their life force is depleted. The castor will them feel a cold, hard weight over their heart. This is where the magical 'core' resides, the thing that allows humans to convert energy for magic. In permanent cases, casters feel a shattering sensation during this stage. The cold sensation does recede but for permanent situations they feel a sense of emptiness. Nothing has fixed a broken core. Its believed the body breaks it to safe it
Magic is broken into groups for this reason. A beginner, while not to trifled with as the coven or mentor will most likely be nearby, can do little more than light a candle and cast petty hexes. Older castors are much more dangerous.
Witches can live for centuries as the body readjusts itself to accommodate the casting and produces more of the needed life force. Even a witch with a damaged core can live a long life as it takes time for the body to readjust
There are limits and rules surrounding magic. Magic cannot do everything. It cannot heal every illness, it cannot fix every hurt, it cannot go against nature. For magics such as controlling the weather, unless it is a creature that naturally has that ability, a large coven is needed. Same with large curses that would cause a a large change. Somethings, once done cannot be undone.