Metamagic

Metamagic is a game mechanic created in Dungeons & Dragons 3rd Edition. As the name implies, it is a way for spellcasting classes (wizards, sorcerers, clerics, druids, etc.) to get even more powerful by tinkering with certain aspects of their spells, augmenting them in various ways, such as removing the need for certain components, expanding their area of effect, and so forth.

While it was truly introduced in 3rd edition, it has its roots in a number of older spells from still older versions of the game. Notably, spells like sequencer and contingency, only some of which survived metamagic, gave casters the ability to play with their spells and fiddle with their output.

In 3rd edition, metamagic was handled as a family of feats that casters could pick up. Each metamagic feat represented a specific magical trick that a caster could apply when preparing or casting a spell, depending on their casting style, and usually with some drawback - mostly in the form of requiring a higher spell-slot than before. Multiple metamagic effects could be stacked on the same spell, but this could get prohibitively expensive in terms of spell slots. You could throw a massive fireball with a huge area of effect that not only maximized the damage instead of rolling for it but also increased it by 1.5 times, but it would require the same spell slot to prepare as a wish spell.

Notably, the famous Quicken Spell metamagic allowed character to break action economy, throwing spells around as one action less than their normal casting time, making it powerful and infamous despite the staggering four spell level hike. Also, divine casters had access to Sacred Spell, to let them penetrate any kind of resistance because fuck you, as a component of their infamously powerful status.

Some metamagic feats could be taken multiple times. Most prominently, the Energy Substitution metamagic feat, which was broken up into five subfeats; Acid, Cold, Electric, Fire and Sonic. Each version of Energy Substitution taken allowed the caster to replace the normal energy type of their spell with that feat's type; Energy Substitution (Acid) could be used to create a Chain Lightning spell that did acid damage, whilst Energy Substitution (Cold) could be used to create Fireball spell that did cold damage.

Notably, it was much harder to use for spontaneous caster compared to prepared ones for... reasons. Reasons that may have started with a mixture of sloppy editing and unreasoning paranoid about the power of spontaneous casting vs. the traditional kind and turned into spiteful malice and an editor/author trying to win a long-lost forum argument in the transition from 3rd edition to 3.5 with the ultimate rules-beating stick. For example, while a wizard who wished to cast a reach shivering touch spell for maximum cheese had only to have the Reach Spell feat and access to the fifth level slot necessary and prepare it thus, a sorcerer who wished to do the same must not only have the slot and the feat, but spend a full round action to make it go off. This also meant that Quicken Spell was useless to a spontaneous caster.

Happily, limited salvation was to be found in the form of Rods of Metamagic! These not-at-all-phallic-and-why-would-you-think-that magic items were each attuned to specific metamagic feats, and could apply metamagic to spells for free a limited number of times per day, requiring neither a spell-level hike nor, in the case of spontaneous casters, a full-round action. Said rods typically came in three flavors of potency, with lesser rods only working on the weakest spells and only greater rods helping out with the big boys.

Metamagic vanished in 4th edition, because it just didn't quite work with the new paradigm to how spells worked. Its spirit lived on in the form of various feats that provided permanent innate augmentations to different spells in a broad sense.

Pathfinder kept most of the 3rd edition metamagics, adding in a few of its own. Energy Substitution was now a feature of specific classes, though. One trait (a form of "half-feat" the game introduced), called Magical Lineage, let a character pick one spell and reduce its effective level by one while applying metamagic to it. This was, by what we're sure is pure coincidence, half the effect of the infamous 3E but not OGL feat Arcane Thesis. Also introduced were Selective Spell, which allowed people throwing AoE's around to exclude their party members, and Intensify Spell, which doubled the level cap for spells that rolled extra dice for caster level. The latter in particular is much beloved by the whole magus class that needs shocking grasp and/or snowball to function on par with others in their intended role.

While the problems spontaneous casters have with metamagic were almost intact (quicken spell however actually works!), a number of cheesy tricks and character options helped mitigate it, such as the Arcane sorcerer bloodline.

It returned in 5th edition, now relegated to a class feature for the Sorcerer, which could burn "sorcery points", a pseudo-mana system, when casting a spell in order to activate metamagic effects; sorcerers can now choose which metamagics they learn as they level up. Unfortunately, due to various issues...namely, how few sorcery points they get, the fact sorcery points are also used to replenish depleted spell slots, and the fact that sorcery points only recharge on a long rest... well, it makes metamagic a lot less useful in 5e than it was, which has upset many sorcerer fans. They also don't get nearly enough choices nearly often enough.

Also, while certain combinations are still very potent (Twinned Spell + haste = best combat buffer in the game for levels to come), and collapsing Still Spell and Subtle Spell into one power that also goes off very cheaply is very, very nice, Quicken Spell, though still good, is hurt by the game's mechanics. Since there's a hard cap of one spell and one cantrip per round, no more, it's a good but not abuseable trick. This is good in a vacuum, but a bit of a pain for a class that could really stand a few more abuseable tricks to its name.

It's telling that the Lore Master Arcane Tradition for wizards in Unearthed Arcana didn't once mention the word "metamagic", and yet it still manages to blow sorcerers out of the water in terms of being able to tweak and modify spells on the fly for greater efficiency in battle; its very first feature, Spell Secrets, lets it change elemental damage typing for its spells at will - which is considered broken in and of itself, because that's a category that includes Force damage, which practically no enemy resists - and also change the saving throw required of 1 spell per encounter, which means they can spontaneously tailor a spell to strike a particular weakness of a creature that would normally be heavily resistant to it due to having a good saving throw. Then, at level 6, its Alchemical Casting lets it modify certain spells by burning an extra spell slot; give up a 1st level spell slot when casting a spell that inflicts damage for +2d6 bonus Force damage, give up a 2nd level spell slot when casting a ranged spell of at least 30 feet to instead upgrade its range to 1 mile, and give up a 3rd level spell slot when casting a spell with a saving throw to increase its DC by +2. Level 10's Prodigious Memory feature lets a Lore Master use a bonus action to swap one of its memorized spells out for a prepared spell instead once per encounter, which would be toe-stepping harder if sorcerers weren't already sucking so hard in terms of spell output per day and actual versatility. Things come to a cap with its ultimate subclass feature: level 14's Master of Magic, where, 1/day, the Lore Master can choose to cast a single spell from any other class's spell list. Which, admittedly, would be more impressive if the spell-lists didn't boil down to "Wizard, Cleric, and token tweaks to either of the aforementioned".

Fans of the sorcerer were outraged, prompting such a backlash that the School of Invention, what many believe to be the 2nd iteration of the Lore Master, was portrayed as a Wild Mage/Artificer hybrid with a theme of "bumbling gnomish know-it-all". Even so, the whole fact that the Lore Master's old design used to be stupidly powerful was subtly mocked by fluff for them implying that they're not nearly the clever magic masters that they think they are.

So, naturally, they never again oh wait!

Metamagic Feats

The first Metamagic Feats were seen in the Player's Handbook, which gave us the now iconic lineup of:

• Empower Spell: +50% to all variable numeric effects.
• Enlarge Spell: Doubles range.
• Extend Spell: Doubles duration.
• Heighten Spell: +1 to effective spell level.
• Quicken Spell: Cast this spell as a free action.
• Silent Spell: Removes the need for Verbal components.
• Still Spell: Removes the need for Somatic components.
• Widen Spell: Doubles area of effect.
• Maximise Spell: All die are cast at maximum value.

However, Wizards of the Coast knew that they had something special on their hands, so a considerable number of metamagic seeped into the games in drips and drabs through the various splatbooks.

THe Player's Handbook II gave us:

• Blistering Spell: A fire-spell exclusive metamagic that buffs the damage by +2 per spell level and causes it to leave an -2 attack & ability check penalty until the end of your next turn.
• Earthbound Spell: Turns the chosen spell into a mine, basically. You designate a spot on the ground when you cast, and the spell waits to go off on whatever dumb bastard steps there.
• Flash Frost Spell: A cold-and-AOE-spell exclusive metamagic; +2 damage per spell level, ad creates a slippery slick of ice across the AOE for 1 round.
• Imbued Summoning: A Summoning metamagic spell that causes the critter you summoned to be under the effects of a 3rd level or lower touch spell of your choice when they appear.
• Smiting Spell: Channels a touch spell into your weapon; great for gishes.

Lords of Madness, the Aberration spell, has the Ocular Spell feat, which lets you cast your spells as cool eyebeams.

Races of the Dragon has two "meta-metamagic" feats in the form of Accelerate Metamagic and Practical Metamagic, both of which are exclusive to spontaneous casters with the Dragonblood subtype; the former lets you ignore the time penalty caused by using one specific metamagic, and the latter can knock off one "spell level penalty" of using metamagic.

Libris Mortis features

• Energize Spell (+50% damage to undead)
• Enervate Spell (+50% damage to living)
• Fell Animate (spell's casualties turn into zombies)
• Fell Drain (spell inflicts 1 negative level)
• Fell Frighten (creatures damaged by spell are Shaken)
• Fell Weaken (creatures damaged by spell suffer -4 STR).

The Book of Exalted Deeds has

• Consecrate Spell (adds Good descriptor to spell)
• Nonlethal Substitution (spell damage is nonlethal)
• Purify Spell (adds Good descriptor, spell does half damage to Neutral targets and no damage to Good targets).

The Book of Vile Darkness naturally counterpointed with the Corrupt Spell and Violate Spell metamagics, which turns half the damage the spell inflicts into Unholy Damage or Vile Damage respectively.

The Consecrate and Corrupt Spell feats would show back up in the Complete Divine, along with the new metamagic feats

• Rapid Spell (decrease casting time)
• Reach Spell (touch spell becomes a 30ft ray)
• Transdimensional Spell (no penalty to magicing incorporel, ethereal or shadow critters).

Now, you'd naturally expect the Complete Arcane and Complete Mage books to have plenty of new metamagic toys right? Surprisingly, Complete Mage only has the one new metamagic in Retributive Spell (spell auto-casts on anyone who hits you in melee). Complete Arcane, on the other hand...

• Black Lore of Moil: Adds bonus negative energy damage to necromancy spells.
• Born of the Three Thunders: Apply to a spell that normally does either Sonic or Electric damage to make it do both damage types simultaneously.
• Chain Spell: Spell affects secondary targets, similarly to a Chain Lightning spell.
• Cooperative Spell: Cast this spell in conjunction with other casters to boost Save DC and caster level checks.
• Delay Spell: Spell's effects are delayed 1-5 rounds.
• Energy Admixture: Elemental Damage Types spell does two damage types simultaneously.
• Energy Substitution: Change the Elemental Damage Types of spell.
• Explosive Spell: AOE spell also pushes targets.
• Fortify Spell: Boosts spell's ability to punch through spell resistance.
• Lord of the Uttercold: Cold damage spell deals half negative energy damage.
• Persistent Spell: Fixed/Personal range spell lasts 24 hours.
• Repeat Spell: Spell you cast recasts itself the next round.
• Sanctum Spell: The spell is more powerful in a specific location, but weaker elsewhere.
• Sculpt Spell: Alter's spell's area of effect.
• Split Ray: +1 target with a Ray spell.

In addition to all of these, the Complete Arcane also features reprints of Nonlethal Substitituion and Transdimensional Spell, as well as the "Sudden" versions of the OG metamagic spells; these let a caster apply their specific metamagic effect "on the fly", without needed to prepare that spell with that metamagic effect beforehand or without boosting their casting time if they're a spontaneous caster. The downside is that it can only be done once per day, which makes them largely pointless.

Cityscape added three new metamagic feats, plus reprinting Sculpt Spell:

• City Magic: Half the damage of an energy spell becomes untyped and irresistable.
• Deceptive Spell: Spell's apparent origin point becomes wherever you wish.
• Invisibile Spell: Spell's effects become invisible.

Frostburn added the Piercing Cold metamagic, which makes a Cold spell so utterly cold that it ignores Cold Resistance and still does 1/2 damage to creatrues with Cold Immunity.

Sandstorm would follow suit with oth Searing Spell, the Fire counterpart to Piercing cold, and Fiery Spell, which simply grants +1 damage per die to a Fire spell and is basically an inferior version of the Blistering Spell metamagic.