So, for those of you who don't know, Onyx Path (formerly White Wolf) have been going back and remastering all of their old games in the New World of Darkness (now known as the Chronicles of Darkness) to fit an updated version of their Storyteller system. Having already tackled Vampire and Werewolf - to great success in my opinion - the next game in line was Mage, probably their most clunky and convoluted creation.
First, I'll talk about the most important mechanic: the spellcasting system. Like I said, it's weighty and value-heavy but not exactly complicated. Every spell has a number of different factors to consider: Potency, Duration, Scale, Range, and Casting Time. By default, every spell produces a one-die effect, lasts for a single turn, affects a single subject or small area, has a touch range, and has to be cast in a ritual (which takes 3 hours for a Gnosis 1 character). However, each spell also has a Primary Spell Factor (either Potency or Duration) that gets a free boost equal to the Arcanum-1. Factors can be changed in a number of ways. You can increase any factor, which also adds a penalty of the casting roll. You can also spend what are called Reaches to dramatically alter the spell, letting you do things like cast in instantly, magnify a given factor, change the primary spell factor, etc. You get a number of free reaches based on your Arcanum dots and the level of the spell you're casting; beyond that, every reach increases the chance of a spell inflicting a Paradox. Paradoxes are more interesting now - either you contain it and let the anti-reality burn out your insides or let it run loose, in which case successes on the Paradox roll give the Storyteller their own Reaches with which to warp your spells effects. You can add dice to your casting roll and lower the chance of a Paradox by using yantras, which can be anything from traditional Order tools to symbolically-important environments. There's a few things I'm leaving out, but you get the picture. You'd definitely want a piece of scratch paper to keep track of all of the factors and modifiers, but it's otherwise rather straightforward.
Attainments are my favorite addition to the magic system. For every dot you have in an Arcanum, you get a cool effect. At one dot, you can instantly counter any spell being cast with that Arcanum. At two dots, you get a useful minor utility, like the ability to cast spells at sympathetic range for Space or the ability to passively detect ghosts for Death, and a unique form of Mage Armor. At three dots, you can summon Supernal entities with greater specificity. At four dots, you get a much more powerful utility, like the ability to automatically resist any magic that would alter your body with Life. And at five dots, you can create your own spell rotes. Mage Sight has been reworked as well and now has two modes: Peripheral and Active. Passive Sight allows you to pick up on any active magic in the area, while Active Sight lets you use your Arcana to glean much more detailed information. For example, Time lets you know everyone's Initiative ratings and predict exactly if and when they're going to act, while Forces detects motion and highlights any hazardous energies.
The lore has not been changed to dramatically, except for them ditching the whole Atlantis thing. The emphasis is now on the nebulous and ahistorical Time Before [the Fall], during which something like Atlantis might have existed, but the reality of Atlantis is now explicitly non-canonical. The Diamond Orders still claim to be the descendants of an ancient - and possibly fictional - Awakened civilization, but canonically, they all emerged during the Hellenistic period. There's a crossover Mage-Werewolf setting in the works that's set in Neolithic Serbia circa 5500 BCE, taking place after the Fall but before both the rise of the Orders and the Sundering of Pangaea, which complicates the series' admittedly ephemeral timelines in an incredibly interesting way.
First, I'll talk about the most important mechanic: the spellcasting system. Like I said, it's weighty and value-heavy but not exactly complicated. Every spell has a number of different factors to consider: Potency, Duration, Scale, Range, and Casting Time. By default, every spell produces a one-die effect, lasts for a single turn, affects a single subject or small area, has a touch range, and has to be cast in a ritual (which takes 3 hours for a Gnosis 1 character). However, each spell also has a Primary Spell Factor (either Potency or Duration) that gets a free boost equal to the Arcanum-1. Factors can be changed in a number of ways. You can increase any factor, which also adds a penalty of the casting roll. You can also spend what are called Reaches to dramatically alter the spell, letting you do things like cast in instantly, magnify a given factor, change the primary spell factor, etc. You get a number of free reaches based on your Arcanum dots and the level of the spell you're casting; beyond that, every reach increases the chance of a spell inflicting a Paradox. Paradoxes are more interesting now - either you contain it and let the anti-reality burn out your insides or let it run loose, in which case successes on the Paradox roll give the Storyteller their own Reaches with which to warp your spells effects. You can add dice to your casting roll and lower the chance of a Paradox by using yantras, which can be anything from traditional Order tools to symbolically-important environments. There's a few things I'm leaving out, but you get the picture. You'd definitely want a piece of scratch paper to keep track of all of the factors and modifiers, but it's otherwise rather straightforward.
Attainments are my favorite addition to the magic system. For every dot you have in an Arcanum, you get a cool effect. At one dot, you can instantly counter any spell being cast with that Arcanum. At two dots, you get a useful minor utility, like the ability to cast spells at sympathetic range for Space or the ability to passively detect ghosts for Death, and a unique form of Mage Armor. At three dots, you can summon Supernal entities with greater specificity. At four dots, you get a much more powerful utility, like the ability to automatically resist any magic that would alter your body with Life. And at five dots, you can create your own spell rotes. Mage Sight has been reworked as well and now has two modes: Peripheral and Active. Passive Sight allows you to pick up on any active magic in the area, while Active Sight lets you use your Arcana to glean much more detailed information. For example, Time lets you know everyone's Initiative ratings and predict exactly if and when they're going to act, while Forces detects motion and highlights any hazardous energies.
The lore has not been changed to dramatically, except for them ditching the whole Atlantis thing. The emphasis is now on the nebulous and ahistorical Time Before [the Fall], during which something like Atlantis might have existed, but the reality of Atlantis is now explicitly non-canonical. The Diamond Orders still claim to be the descendants of an ancient - and possibly fictional - Awakened civilization, but canonically, they all emerged during the Hellenistic period. There's a crossover Mage-Werewolf setting in the works that's set in Neolithic Serbia circa 5500 BCE, taking place after the Fall but before both the rise of the Orders and the Sundering of Pangaea, which complicates the series' admittedly ephemeral timelines in an incredibly interesting way.