What's GLΔG? Read here. In short, "character advancement" through narrative triggers. These aren't quite the same as GLOG classes, since theoretically one could finish all of them (though this could take a while).
It's safest to begin as an apprentice to another Magician, but nothing prevents a young Wise One with more talent than sense from experimenting alone.
Find an object of Power; usually a grimoire which has passed through many hands, but perhaps the skull of an archmage or a gem that whispers to you in the back of your skull. If you lose it, find another.
You are a magician of the first rank. Other magicians recognize you, and you recognize them. You can detect magic by scent, taste and touch. If you meet Death you recognize him immediately. If you can't grow a beard you should buy a fake one or the other magicians will make fun of you.
Keep a staff (at least as long as you are tall) by your side for a month. It may rest by you as you sleep or lie in the back of your cart, but if you relinquish it in any meaningful way, start again.
Hold your staff up before you, mutter some magical syllables, and light as bright as a torch blazes from the tip. The light shines until you stop muttering or allow the staff to touch the ground.
With greater power, this is sunlight which blinds or destroys dark things vulnerable to it.
Form a padlock and key from a kilo of silver (expect this to cost as much as a good horse), and place the key into the lock. If anyone removes the key from the lock, scrap them and start again with fresh material.
If your padlock is locked, mundane doors lock with a touch; if your padlock is unlocked, mundane doors open with a touch. When your padlock changes states all doors you have cast this on change to match. Operating the door with its real key ends the effect.
With greater power, you can slam mundane doors or burst them open with a pointed finger and a shout. With supreme power, you may choose to destroy doors instead of opening them, and doors you close can only be opened with violence.
Spend a full day, without sleep, completely blinded by a fogbank. Certain mountains can be relied upon for this. If the fog clears, start again.
Huff, puff, and breathe out. Every round, exhale about twenty liters of fog. Circular breathing helps here. Your fog disperses with five minutes of direct sunlight or brisk wind, or a few moments after you stop breathing it out.
With greater power, this fog can be impenetrably obscuring, like cotton batting, and unbreathable for creatures not yourself. With supreme power, this fog can be unbreathable for you and lethally toxic for others.
Heave around as much silver in a sack as you can physically lift for a full week. Speak to it as if it were a close friend of yours. If it touches the ground, or someone refers to it as a sack of bullion and you do not argue, start again.
At your command, an invisible force will follow you for eight hours. It can carry as much as you, and while it prefers wheelchair ramps it may climb stairs veeeery slowly. This force refuses to work more than eight hours in a day.
With greater power, this force is as spry as you are (or as you were, if you're now old and arthritic), and can easily keep up with you even when carrying a full load of treasure. It may carry things to and from an area if you wish, but it still won't work for more than eight hours a day.
Keep a wand (at least as long as your forearm) by your side for a month. It may rest by you as you sleep or wait in a sheathe under your clothes, but if you relinquish it in any meaningful way, start again.
Wave your wand before you, shout a magic syllable, and a bolt flies from the tip. It strikes a point you choose, unerringly, as if with your closed fist.
With greater power, this is a bolt of supernal force which may disrupt spells and punch ghosts.
Become fucking ripped. If using 3d6-generated stats, you're going to need at least a 15. The old-fashioned way works, but if you have magic to make you (permanently) buff that will also suffice.
With a series of magical gestures, you may move small objects with thirty feet of you as if you held them in your fingers. This doesn't apply enough motive force to deal damage with melee weapons (they desync from your control and fall), but you could pull a trigger, or draw a razor across someone's throat. You drop the object immediately when you stop making the gestures.
With greater power, this moves objects you can see as if you were carrying them across your shoulders. This does apply enough motive force to deal melee damage, and can fling furniture or toss people around.
(1) Disguise Self
Change your name to something appropriately magical, like Xodorn, or Radamandafandalaster, or Thubarin Thorpein III. Destroy all references to your old self. If another is discovered you know of it immediately, and must destroy it before using this ability again.
By applying a paste of cold cream, fine albero and oil-of-roses, you may drastically change someone's appearance. You can alter apparent age, gender or race, and alter height by an inch or weight by twenty pounds or so.
With greater power, you may disguise someone as any living creature larger than a hobbit and smaller than an orc. With supreme power, you may disguise objects and terrain in a similar manner.
(2) Greater Power
There are many ways to gain more power... you could sacrifice a virgin and let their blood flow onto your object of Power, eat the heart of a Greater Magician, or gain the patronage of an Alien; but you could find other ways.
You are a magician of the second rank. Your hair is now white and your eyes are now unusual in some way (your choice), and weaker magicians fear you. Mundane creatures who lock eyes with you cannot break eye-contact until you blink. Unciphered text is readable to you with strenuous study, even if you don't know the language. You can grow a beard, even if you couldn't before.
Learn how to brew a potion of Living Death, drink it, voyage to the land of dreams, steal an eye from its queen. In the waking world this is a pink pearl. If you lose it you must find another.
Those who speak to you for at least a minute fall into a deep and dreamless sleep, if you wish. This is natural sleep from which they will wake in eight hours if not awakened, and you may only affect one person at a time.
With greater power, you may cause someone to sleep with a shouted command, or lull them into permanent (until dispelled) stasis with at least a minute of conversation. With supreme power, you may apply this to as many people who can hear you at once.
For a year and a day, do not interact with thinking creatures. If any see your form or hear your voice, start again.
While concealed under a hooded robe, no one takes notice of your presence unless specifically looking for intruders (or weirdos in hooded robes).
With greater power, you cannot be seen if you do not wish. With supreme power, you cannot be detected in mundane ways, until someone actually bumps into you.
Throw a dozen creatures, at least as large as a child and possessing enough intelligence to brace for impact and scream, from a cliff at least one hundred feet high. Record their behavior and the results. If you lose your notes, start again.
With a series of magical gestures, a falling object has 1% of its actual mass until you stop performing the gestures or it touches the ground. The law of gravity dictates that it theoretically fall at the same speed as before, but in edge cases like humans in air buoyancy becomes an important force.
With greater power, you may reduce a falling object's mass to 1% of 1%, causing most things to float up like a balloon. With supreme power, a creature affected by this spell may (if you wish) move perpendicular to the ground at walking speed.
(2) Hideous Laughter
Laugh until your voice is a half-whispered rasp and you're coughing blood. When it heals (three days at first, up to a week eventually), start again.
You can force another creature to imitate your cackling laughter, preventing both of you from speaking or whispering magic syllables for as long as you laugh.
With greater power, this prevents them (but not you) from holding objects or making magical gestures. With supreme power, as many creatures as you wish will imitate your laughter if they can hear you.
Form an hourglass from glass and a kilo of gold, and fill it with precious stones to serve as sand (expect this to cost about 100 times the lock-and-key, or a prince's ransom). The hourglass functions if kept hidden somewhere, so long as you know where it is. If you lose or break the hourglass, start again.
If your hourglass is right-side up, you may move and think in double speed at-will. If inverted, you may move and think at half speed at-will.
With greater power, you may apply this to another creature instead of yourself. With supreme power, you may fine-tune the flow of time between ten times slower and ten times faster for the affected creature.
(2) Powerful Word
Learn an ancient word in the Occulted Language. Before you can speak it, tattoo its hanzi on your tongue. If you have no tongue, tattoo it inside your throat.
With a shouted word, inflict a moment of agony in all those who hear. The deaf are unaffected; those with the word's hanzi tattooed behind their ears understand what you are saying.
With greater power, your pronunciation shifts, and this word may stun for a full minute — but as you know it's coming, you are only stunned for about ten seconds. With supreme power, this word instantly kills mortals, no save.
(3) Supreme Power
There are a few ways to gain this power... you could sacrifice a legendary fighter, a master thief and a powerful wizard and allow their blood to flow onto your object of Power, eat the heart and eyes of a Supreme Magician, or sell your soul to an Alien; there are other ways but they will be very difficult.
You are a magician of the third rank. Your eyes see in darkness. Animals and small children hate you instinctively. You do not age, and while your beard grows down to your heart you cannot be reduced below zero hitpoints. Elfs and other elder-things offer grudging respect.
Vivisect a bull, a bear, a cat, a fox, an owl, an eagle, and an additional six creatures as sapient as you are, and record your findings. If you lose your notes, start again.
With several hours of careful tattooing, and a sharp blow to the base of the skull, you may alter the form of a living person (including yourself). You may set their physical stats to any value you wish, change their apparent age, gender and race, or some combination thereof. Anyone capable of Polymorph can reverse these changes, effortlessly if the tattoos remain and with study and care otherwise.
With greater power, you may Polymorph animals or turn humans (physically) into animals. With supreme power you may alter mental stats as well, and insert, alter or remove memories.
Be struck by lightning, survive, and be struck by lightning again. If you die, start again.
With a series of magical gestures you can generate a fistful of cracking sparks. They will discharge, painfully, with skin contact or when a metal object you are holding hits a metal object someone else is is contact with, and dissipate when you stop making the gestures.
With greater power, the point into which the sparks discharge is probably struck by lightning, weather permitting. With supreme power the sparks leap forth of their own volition, badly scorching their target and siderating it from a clear blue sky
Feed someone important to you into a bonfire. If they live, start again.
You know how to create an alchemical substance which, when heated or struck or looked at funny, burns near-instantly in a bright flash and a loud snapping sound. It can only be (safely) transported in a container of water. When poured on the ground in sufficient quantities this creates a terrifying wall of fire for a few moments. When dried into a tiny pellet it may be flung from the hand or a sling for a frightening bit of fire-working.
With greater power you may (safely) form this substance into charges the size of an apple, which explode like grenadoes when thrown. With supreme power your blood, if mixed into the substance, prevents it from exploding until you will it, allowing you to (safely) use large amounts of it to undermine walls or burn crowds of people to death.
Become really, truly, totally lost for a year and a day. If you learn where you are or are spoken to in your native tongue, start again.
With a series of gestures, rip the seams which hold time and space together. If done carefully this won't draw the attention of anything powerful and unpleasant. You may use this tear in reality to scry into places you have seen before, or which can be clearly described to you. The tear is visible from the other side. Nearby Magicians may be able to sense its creation.
With greater power you may, over the course of several weeks, build a ritual gate from large amounts of precious metals and stones. This allow you to tear more stable holes in reality which are large enough to be walked through. If there is a gate on the other side you may travel back and forth freely, otherwise it is a one-way trip. The target location of the gate may be changed in an hour-long ritual. With supreme power the gate needs not lead to anywhere real; it may instead open onto a private demiplane, whose physical laws are yours to command. This makes learning other spells easy. It also makes you vulnerable to the Old Things that live Outside, swimming in illimitable gulfs of night and darkness where the dead do not rest and the living do not survive.
You could develop your spells without ever becoming a Greater or Supreme Magician — but this is increasingly impractical as you grow in age and number of enemies. And really, the benefits far outweigh the costs. Were you even using that soul?