Dungeons & Dragons: All Mage Subclasses, From Most Powerful To Most Powerful
Wizards are the most classic spellcasters in Dungeons and Dragons, and they have a lot of great subclasses to choose from.

Dungeons and Dragons: Honor Among Thieves has once again got people excited about the iconic tabletop franchise. Judging from the trailer, it appears that the infamous Red Wizards of Thay are the enemies of the Band of Heroes. Their display of power may have persuaded some novices to try wizarding lessons.
Some good news, mages don't have really "scary" subclasses, since mages are by default one of the most powerful pure classes in the game. That being said, some subclasses are really starting to enter game-breaker territory due to their idiosyncrasies.
13/13 Transmutation

This subclass sounds pretty cool on paper. Altering states of energy and matter for the wizard's own means is the type of reality shifting any magic spellcaster should aspire to. The raw materials for creation are at your fingertips. Unfortunately, it's not that impressive in practice.
Minor Alchemy is neat, but ends up being a novelty in most campaigns. The Transmuter's Stone provides a strong but low energy stone that grants different buffs to its bearer. shapechanger is a free Polymorph spell limited to CR 1 variations. Master Transmuter also offers some great features, sadly below Potential for other subclasses. Far from useless, but not the "Fullmetal Alchemist" most people expected.
12/13 Conjuration

Magician is slightly better than Shapeshifter, because it actually creates things out of nothing, rather than needing some kind of material to work. The junior spell is more versatile than metamorphosis, as it allows the creation of anything no larger or larger than 3 feet and weighing no more than 10 pounds. The item dissipates after taking or dealing damage.
Creative players will find this has a lot to do with it. Benign Transportation provides a free Misty Step every long rest, and adds the versatility of being able to swap with medium sized or smaller willing creatures. This effect can also be used after casting a summoning spell of 1st level or higher. Focused Conjuration prevents the Summoner's concentration from being interrupted by damage, while Durable Summons give any summons an additional 30 health. These are solid effects, but nothing groundbreaking.
11/13 Graviturgy

Wizards are always messing with the boundaries of reality, and gravity is one of the laws they most often break. Gravity is a theoretically powerful course Rely on concentration. Adjusting the density allows doubling or halving the weight of an object or creature, conferring different benefits (and drawbacks) to the two states.
Gravity Well, without any checks, allows a mage to move a target 5 feet in any direction after a spell hits or a saving throw fails. Violent Attraction increases the speed of attacking or falling, which in turn deals bonus Strength damage. The apex event horizon forces creatures within 30 feet to use gravity to hold people in place while dealing massive force damage. If the centralization requirement is lowered, they risk going head-to-head with some top-level subclasses.
10/13 Necromancy

Necromancers, a previously mediocre class, are saved by Tasha's new spells. Before they didn't have enough support to stand out, but now they are in a good position. Grim Harvest allows necromancers to steal life from dying creatures. Undead Thrall makes resurrected undead hit harder and take more damage.
Inured to Undeath prevents reducing a person's maximum health and resistance to necrotic damage. Finally, Command Undead allows the necromancer to use magic to control any undead, even the undead Under the servitude of other wizards. Situation, but could be hilarious if the boss's big minion happens to be a low INT undead. Despite the guts, it's a solid class.
9/13 Evocation

While most power gamers would balk at the idea of a damage-focused wizard, they're still wizards who shoot fireballs with impunity. Few creatures survive such an onslaught, save for those the wizard chooses to save with a sculpting spell. Powerful cantrips ensure that cantrips always deal damage, even if the enemy succeeds on a saving throw.
Arcane Summoning allows wizards to add their Intelligence modifier to their summoning spells. Finally, the Overchannel makes it possible for any evocation spell cast from 1st to 5th levels to deal a single burst of maximum damage with no adverse effects. After using this ability, the wizard will suffer severe necrotic damage that ignores immunity and resistance. Overall, if lacking in versatility, it's a great subclass for every magic spellcaster fire fan.
8/13 War Magic

War Magic is the "gatekeeper" of a consistently powerful subclass. There's nothing wrong with it, nor any glaring downsides. However, it doesn't do any harm either. Arcane Deflection greatly increases survivability thanks to +4 saving throw and AC bonus, at the cost of being unable to cast level spells next turn.
Tactical cunning is a gentle boost to initiative. Power Surge is not as powerful as Evocation in terms of damage, but is useful against Counterspell and Dispel Magic and is a nice bonus. Persistent magic grants a fixed bonus to AC and saving throws while concentrating, ensuring that they never break concentration. Finally, Deflection Shield increases the damage of Arcane Deflection. Overall, solid features that won't break the game, but make the Warcaster very reliable.
7/13 Illusion

Magicians are powerful wizards who are limited only by their own creativity. However, the subclass does take some time to get into "powerful" territory. The improved Minor Illusion is now equipped with state-of-the-art sound technology. Malleable Illusions make hallucination spells last a minute or more to change their properties in real time. Illusory Self is a supercharged version of the magic item Cloak of Displacement.
In response, the wizard left an instant copy of themselves in front of them. This guarantees a missed attack. Finally, the feature that takes Illusion School to greater heights is Illusion Reality, which turns any illusion into reality A minute, an eternity of fighting. The only caveat is that it cannot be animated, magically, or deal damage directly. A boon for the creative player, and the DM for giving. Handicapped due to not being as powerful as other wizards in the early game.
6/13 Enchantment

The Enchanters are the premier gaslighters of the fantasy world. This subspecies is good at incapacitating enemies and turning them against each other. The hypnotic gaze immobilizes the target creature, entering a mesmerizing trance, as long as the mage is within 5 feet of the target creature. Instinct Charisma causes the attacker to attack creatures near the wizard instead of the wizard himself.
Split Enchantment is an incredible spell that basically twins enchantments like Haste and Enlarge/Reduce for free. Altering memories is perhaps a powerful but somewhat disturbing pinnacle feature that keeps creatures from realizing they're enchanted in the first place. In political campaigns, it's a utterly broken force, and in the heat of battle, it can cause endless chaos. Think Jessica Jones' Kilgrave from the MCU, but with a dangerous wizard spell.
5/13 Order of Scribes

When people say wizards are spellcaster nerds, they are who they imagine. Order of Scribes has a Wizardly Quill that requires no ink and faster spell transcription. Their spellbooks are also enhanced, gaining arcane sentience. One spell's damage type can be substituted for another spell's damage type, and each long rest skips a ritual casting time.
Manifest Mind gives wizards the ability to summon echoes of their tome wisdom, which can be considered "duplicates" of the spellcaster. A great positioning tool. Master Scrivener allows creation of magic scrolls of level 2 or lower once per long rest. Finally, One With the Word has an advantage on all Intelligence checks and has a unique damage negation (at the cost of temporarily losing some spells). A subclass that elevates everything that makes a wizard so powerful.
4/13 Abjuration

Spellcasters are known to be "slimy", so anything that helps them survive is very welcome. Abjuration is specifically for this. Arcane Ward weaves protective magic around the mage, blocking incoming damage, and it has hit points equal to twice the mage's level plus the intelligence mod. Once health drops to 0, it can be recharged by casting more protection spells.
Projected Ward allows wizards In response, temporarily offer ward protection to allies. Improved Protection adds a proficiency bonus as a modifier to protection spells. Finally, spell resistance is immediate resistance to spell damage and gives advantage on saving throws against all spells. A clunky subclass of an otherwise not so clunky class.
3/13 Bladesinging

Most wizards are known as nerdy spellcasters, but Blade & Soul breaks that stereotype, combining martial prowess with magical dominance. Bladesong provides bonuses to AC, Mobility, and saving throws to focus on spells. It also provides advantage on Dexterity checks. Bladesingers also gain bonus attacks, further enhancing their military style. Tricks can be used instead of one of the attacks, perfect for a Booming Blade build.
Song of Defense allows the wizard to sacrifice one spell slot to reduce damage taken, equal to five times the level of the spell slot used. Finally, Song of Victory provides a flat bonus to melee weapon damage via the Intelligence modifier. Bladesingers are all-around versatile casters that can play as support or damage dealers at will.
2/13 Divination

Diviners used to be the most powerful subclass in the game, due to the fact that being able to see the future in Turn-based game. Portent has the player roll two d20s and records the numbers rolled. These then replace any rolls the wizard or other creature made before the outcome. In essence, omens force an outcome in favor of the caster.
Each time a divination spell is cast, the divination expert restores a spell slot of a lower level, up to a maximum of 5th level. Every rest of the third eye grants a perception ability, such as darkvision or blindsight. Finally, Greater Portent gives Portent three d20s instead of two. Even though Portent is the only feature in this subclass, it's still one of the most used features in the game.
1/13 Chronurgy

Chronomancers are by far the worst wizard subclass, and are in contention for worst overall. The timeshift acts as a reaction, forcing creatures within 30 feet to reroll. Time awareness can promote initiative. Momentary Stasis, the temporary bread and butter of the subclass, incapacitates creatures in a magical energy field if the save is failed.
Arcane Abeyance essentially stores spells of level 4 or lower in beads for later use. Convergent Future is a super version of Portent that fully enforces The mage reacts to any roll seen within 60 feet with a success or failure (then gains 1 level of exhaustion). When time itself becomes a plaything, it's no wonder Chronomancer gets so much praise.