In the end, all the characters end up confused and no one really knows what the rankings of the power system actually is.

And if that confused you, basically the system goes like this:

The main character (Quaraun) holds the title of the world's most powerful wizard (currently), but no one really knows how or why he came by that title and he himself doesn't know why people call him that as he does not himself think that he is the most powerful wizard.

Previously however a wizard named Gibedon held the title of world's most powerful wizard.

Before Gibedon held that title, it was held by King Gwallmaiic.

Before King Gwallmaiic it was held by wizard known only as The Ghoul.

The Ghoul was King Gwallmaiic's advisor. But he got too powerful and got banished into a Hell dimension and the portal sealed up so he couldn't escape. Thus the title went from The Ghoul to King Gwallmaiic, as Gwallmaiic defeated the Ghoul.

Gibedon replaced The Ghoul as King Gwallmaiic's advisor, thus took over the title. The two also became lovers.

While Gibedon was out of the country, Quaraun became King Gwallmaiic's lover.

Upon his return, Gibedon discovered the King's new lover, had a fit and tried to kill both the King and his lover. The King ends up seriously wounded. In trying to pull the knife out of Gibedon's hand, to stop Gibedon from killing the King, Quaraun accidentally stabs and kills Gibedon.

With Gibedon dead, the title once again goes back to the King. However, a few weeks later the King dies from the infection caused by his wounds, leaving Quaraun heartbroken at the death of his lover. Quaraun becomes a Necromancer to resurrect the King as a Lich.

Having killed former title holder Gibedon (without using magic to do so) and having resurrected former title holder King Gwallmaiic, Quaraun now gets the title slapped on him.

In actual scale of use of magic it makes no real sense at all, but for the sake of the actual plot, it makes perfect sense in the minds of the simple tavern folk who used conspiracy theories to come up with the whole thing.

In the end, the title of world's most powerful wizard, is more something bards weave into tavern songs, then actual scale of power/skill the individual magic caster actually possess.

I wrote it that way to make sence in the minds of the people in taverns who listen to bards, rather then have it actually make sense to the powers the wizards actually had.

In terms of actual magical ability:

King Gwallmaiic way out powers the other wizards in terms of sheer skill, because he is also a 3,000 year old Faerie that has had many centuries to build that skill.

The Ghoul's son GhoulSpawn, (who is never given the title at all) actually is physically the most powerful wizard in terms of ability to harness energy; this being because he is a Demon and is able to withstand the side effects of spell casting, which other races can not.

In terms of psychic ability, being able to control the elements/weather, and possessing a hive mind telepathy that allows him to gather up armies of plants and animals (with bloodthirsty rose bushes strangling people with thorny vines and trees uprooting and marching across the field to do battle for him), that ability goes to Quaraun, who rightly holds the title of world's most powerful wizard, after he calls up quartz crystals to do battle for him in The Battle of Ongadada, where crystals come to life and embed themselves in every living being, killing 31 billion people across 3 solar systems in less then 30 seconds, by turning them into quartz statues. Quaraun is a wish granting DiJinn, and whenever he wants something to happen, simply says: "I wish...." and it happens immediately. In the case of the Battle of Ongadada he wished the world would die, and seconds later it did.

However, none of these things are taken into consideration for the actual title of World's Most Powerful Wizard. And Quaraun simply has the title because he killed Gibedon and resurrected Gwallmaiic, which is a completely illogical reason for him to have the title, considering the things his is capable of, but such is the logic of the tavern bards who wrote the songs and came up with the title.

Basically, the wizards themselves do not use a scaling system, nor do they care about such things. And the only people who do care about such things are the people who sit around taverns getting drunk and listening to tavern bards. The bards then make up the titles, tossing the titles at random on whatever wizard best fits the song/story they are singing/telling to the crowd. The crowd folk later retell the stories to their families who tell their friends, and sooner or later the story/song will get back to the wizard who'll be clueless as to who slapped him with the title or why.

I particularly like to have the wizards be in tavern scenes, where they are sitting in the crowd, listening to the bard, and the bard is clueless to the fact that the wizard he is weaving tales about is right there listening to him do it. The wizard will be there having a drink with his friends and suddenly be like: "OMG! He's talking about me? But I didn't do that!"

I kind of use it more to show how rumours get spread about the wizards, because usually the stuff bards attribute to the wizards are not things the wizard ever actually did.

So, yeah, like I said, not exactly a system of power scaling, but, it's some sort of a system, one that works with the plot in question at least. :P