How to handle magic in a shared fantasy setting is tricky. Especially if different authors have different ideas of how magic should work.
Here are the principles of magic that we are laying down for Korovia to set the basic tone of the world.
#1. Magic is all around people but they cannot see it because its extra-dimensional energy that comes from other planes of existence.
#2. Magical energy comes in various types: Positive energy (which fuels life) and negative energy (which is commonly used when making undead or death magic), as well as energy found in the 4 major elements (earth, water, air and fire). Beyond this there is also divine energy (used for divinations), anti-magic (used for abjurations and dispelling magic) and several other types.
#3. Most wizards (mystics, sorcerers, etc) won't go into huge details about how the different magical energies work beyond maybe the concept that one type of magic can cancel out other types (eg. anti-magic can cancel out all other types but is otherwise useless as a power source). For wizards it is more about what the spell does rather than how it works.
#4. Low level wizards can't use a lot of magic. Using magic causes the person to tire easily. The more powerful a wizard becomes the more energy they can store without tiring, but it takes them time to study, prepare and memorize spells which can be very complex.
#5. Spells often have material components, a substance needed to cast it. eg. A sleep spell needs sand (as per the Sandman) or something else related to sleeping. Likewise a flying spell might require a feather, a waterbreathing spell the gills of a fish.
#6. Low level wizards have weak spells. They just don't have the ability yet to store large amounts of energy. That requires time and practice. Some exceptionally gifted wizards (eg. Raelean in the Lilith Bloodstone stories) are able to store more energy despite their youth becase of natural talent, elvish blood or other combinations of factors. In Raelean's case he has a triple whammy: Natural talent, elvish blood and he was bathed in magical waters when he was a baby.
#7. When in doubt it is recommended you look at a Dungeons & Dragons book (you can download a free PDF of the 2nd Edition book online easily) and look at what spells a low level wizard can cast. D&D books provide a good reference point and can provide a source of ideas.
ELDRITCH WORDS
Korovia also has something called "Eldritch Words" which are rare and very closely guarded secrets. The words themselves are like command words for a magical object (like saying Open Sesame) except there is no object. Anyone who knows the word can use it if they have a little bit of magical talent and know how to pronounce it properly.
The words themselves produce an extremely minor effect... like lighting a candle or killing an insect. The problem with Eldritch Words is that the more people who know the word the weaker the spell's effect is. If too many people know it then it might only produce a spark and not even a spark strong enough to light a candle. Thus the necessity of keeping them a secret so they remain useful.
Some more powerful Eldritch Words may exist, but they would be considerably valuable and there are quite a few evil wizards who would kill for the knowledge of the word.
A dying person who has an eldritch word will often whisper it to someone in fear of the word "dying" with them.
