Alchemy

Overview

Alchemy is a subset of essence magic that takes established substances and removes their energy, shaping and warping probability to form new structures. In order for this type of magic to work, compatible elements must be used and the alchemist must be sufficiently powerful enough to shape them to their liking. As such, most alchemists go through training in simple manipulation of energy before moving on to probability and finally into true alchemy. This magic tends not to need as much power as outright essence magic and thus is generally practiced by those who has lower magical aptitude. Users of alchemy are called Lodawa. 

Limitations

To work, the materials forced together must be compatible with one another. This is mostly a trial and error process. In general, only non-living things can be combined. The mythical turning lead to gold was done decades prior to the story, although it is a banned practice with alchemists hired by the state to separate various components and dispel suspicious specimen.
Alchemy is built on probability and order. The basic idea is to force a different configuration of elements and build them back in order to form something else. This is mainly a manipulation of probability then the elements themselves, setting it apart from pure essence magic. The most fundamental limitation is that the things being put together must be compatible with one another. Opposing elements will be extremely difficult to work with. This is mostly done through trial and error. A sample of lead, for example, could have several elements in it. To shape it into gold, the alchemist would have to determine what those elements are and then reshape them to combine them with an existing piece of gold with a similar elemental makeup.
If all elements in a sample are directly opposed, no alchemist can force them to combine together. In finding that samples cannot be combined, they will often try to change something about one sample in order to make it more compatible and then work to combine the two. Finally, they would try to use the newly formed material to get to what they originally wanted.