There are 4 main classes of magic: Common, Wizard, Clan, and Throne. The first, Common Magic, is used by many peasants to do simple, everyday things like make a cape clean and dry, or cause hot metal to cool quickly. They make up 57% of those who use magic. The second class, Wizard, is a bit more rare: only about 34% of those who have magic use this type, and at least a quarter of them are nobles. Wizards- although the sub-professions include potion hag and witch as well- can use elemental magic, and occasionally, they may also have the ability to levitate things or teleport. The third class is Clan Magic, which used to include 4 but now includes only 2 different clans: Celestial and Shadow, both of which have limited access- usually 8 gates or less- to Portals in the Portal Realm. The Celestial Clan uses light, sky, and celestial magic, whereas the Shadow Clan generally uses thief or shadow magic, as well as summoning, teleportation, and combat magic. The fourth and final class is Throne Magic. As of right now, there are only 5 people who can use it. They have almost unlimited access to the Portal Realm- only worlds which contain mages stronger then they are are barred to them- and can essentially use almost every kind of magic there is, given enough time to learn it. They are the rulers of the world, at least theoretically, and are half immortal, meaning that they age slower and have a "second chance to live." The only 2 ways they can die are death by pain, as a traditional mage, or by one of the 13 Gray Spells, which can be set off by anyone with magic, wielded by anyone, but can slay anyone and everyone. The way they work is to feed on life force till there's nothing left. However, they prefer those with magic, the stronger the better.
The Portal Realm is a parallel world which gives you access to other worlds, which don't necessarily have the same magic rules.
Death by pain is a traditional mage death in which pain literally overwhelms body and soul and causes a fatal heart attack, among other things. It is caused in one of a few ways. The most common is that magic, while it looks and can feel quite physical, and effects things in the physical world, really targets your mind and soul, where you register pain. Once the pain gets to be to much for your mind to handle, it quite literally kills you. Another way to cause this death is by using up all of your own power, which is also attached to your life force. The last possible cause is use or take in too much power at one time, which gives your mind and life force an overload, and sometimes causes your soul to implode, separating at least part of your spiritual self from your body.
The potions hags can make include poison, love inducer, invisibility, dizziness, hallucination, disguise, element immunity, injury immunity, and wound healing. How effective they are depends on the amount of magic the individual has, but theoretically, to make a potion, all hag would need is knowledge of the recipe.
There are 2 scales in this world called the Power Scale and the Pain Scale, most commonly. The Power Scale starts at 0 and goes into the negatives; the lower the number is, the more power. Someone with no ability to use magic has 0 or sometimes reads as 1, meaning they're not regularly exposed to it. The amount of power varies to each individual, but generally speaking, higher classes have greater power. It is possible to increase your power, but it takes a very long time to get a minuscule increase. However, to try to get a much faster, artificial effect is often fatal.
The Pain Scale generally balances the Power Scale. The more power, the more pain before death. Actually, in most cases it almost lines up. The Pain Scale starts at 50 (which is basically -50 pain) and goes down (-200 on the scale means you're experiencing 200 pain.) 0 is no pain, but you don't have a warm, healthy feeling either. 0 can be described much the same as being completely worn out, but not in pain.
It varies from person to person, but non-magical people usually go from about 30 to -150/200 on the scale. This means the least amount of pain is 30, which is healthy, and the maximum they can withstand before death is somewhere between -150 and -200 (this is actually partly dependent on their personality.) If you spend too much time injured, or experience close to maximum pain multiple times, the minimum number of pain you can feel actually goes down. If it goes below 0, you will be in pain of varying degrees for the rest of your life.

Magic is mostly hereditary, inherited through your physical ancestors. However, there is something called your magical bloodline, meaning that while your body is descendant of one line, your spiritual self is descended from a different line. This being said, only 12% of the main world's population does not have the ability to use magic. However, over 30% percent refuses to use it, saying it is "evil." These people will huddle together in villages where magic is banned, and even go so far as to put up wards which drain mage's powers till it's not usable, and can be fatal for those who try.
There are 3 other groups of outsiders, 2 of which use a form of magic, though it's not "traditional." The nonmagical one is the Banished, who were once evil, magical pirates but were banned from the seas 2 centuries ago, and now roam the wilderness, getting drunk and causing violence and unpleasantness on their path.
The second group is the Riders. They are outcasts of society, and wander in groups of about 8-10 people. The magic they use has to do with speaking to horses, and they train and enchant their horses so that they can run 40-50 miles per hour for a good half hour, at least. They are silent, and keep to themselves mostly, living off the land.
The third group is by far the largest. They are known as the Magicians. They have their own society, made up of 5 hidden cities, which they forbid anyone except other Magicians to enter. They also do not associate with the rest of the world much, although a handful of them live in regular society.