All the Magic Skills found in the Genesys Rulebook are allowed. These skills do not have to be career skills to be accessible, so a character could learn a bit of magic after the fact. However, there must be a compelling reason for a character to learn these arts. This is especially true of Divine spellcasting, which is rare even within the Church.
There are some specialized knowledge skills found in Magma.
Education: this becomes the general knowledge skill, covering science, history and any other subject not covered by the other knowledge skills. Note that historical facts, even if they relate to the religious or the arcane, are still covered by Education.
Scriptures: this covers the knowledge of the Church of the Nine in general. To quote scriptures, remember a fact about thaumaturgy, or identify a spirit as the demon Baphomet, use this skill. This one is usually possessed by the people following the tenets of the Church of the Nine, and not only by priests. This is the skill used in lieu of Knowledge when using Divine spellcasting.
Theories of the Arcane: this covers the knowledge of the arcane such as sources of energies, ley lines, creatures born or infused with magic, elements summoners require to call forth specific entities… This skills is possessed by arcanists, nobles and the odd monster hunter or arcane investigator. This is the skill used in lieu of Knowledge when using Arcane spellcasting.
Old Ways: this covers the knowledge of the natural order of things, elemental spirits, spirits of nature, runes, and elements of Primal magic. This skills is usually possessed by the followers of the old ways. This is the skill used in lieu of Knowledge when using Primal spellcasting.
The Ancients: this knowledge pertains to the old race and/or civilization known as the Ancients. The monoliths and other ruins found all around the world are attributed to them. This knowledge is rare is restricted, only available with game master permission and likely not at character creation. As a special knowledge, the first level is usually rewarded by the GM for making a significant discovery about the Ancients. Further levels could also be a matter of discoveries, or could be purchased with experience points if there is a possibility for the character to study the Ancients from a decent source of information.