Warlock

For Eldar Warlock, see here.

Warlocks are a type of magic spellcaster in fantasy settings. They are also the male counterpart of witches. Compared to others, warlocks are usually dedicated completely to offensive magic and in a few cases, dabbling in the forbidden arts like black magic and daemonology to achieve more power, although this is not always the case.

In Deadlands

In Deadlands, both the generic black magic-using badguy and the PC "huckster" class/archetype/thingy would technically fall under the warlock moniker, and black magicians are commonly called warlocks to boot. Hucksters are a special case in that they literally deal with the devil for their magic; whenever a huckster casts a spell, they astrally project into the Spirit World and offer a passing demon to play a game of skill & chance (poker being, of course, traditional); if the demon wins, it gets a chunk of the huckster's soul (which translates to a huge amount of physical pain and/or death for the huckster), and if the huckster wins, the demon has to surrender the mojo needed to make the huckster's spell a reality. Part of what makes spells differ in difficulty to cast is the some spells either need more juice to work than others or else are calling for stuff the demon wouldn't normally like to do - it's a lot easier to call them up to kill somebitch than to make them protect you, for example.

In Dungeons and Dragons

A Warlock class character.

Instead of gaining their power though meticulous training and study like the Wizard, or natural-born talent like the Sorcerer, they make contracts with very powerful entities and forces and channel that energy, like an arcane Cleric.

1e

In 1st ed AD&D, characters had titles as they leveled up. An 8th level Magic-User gained the title "Warlock." Nobody cared about these titles, not even the people who used weapon speed or the AC to-hit modifiers for each weapon. There was a Dragon magazine article (issue 43) describing a 'witch' npc class, and male npcs that took this class were sometimes called "warlocks" instead.

2e

In 2nd ed AD&D, a character could take a class kit, which was essentially a set of alternate class features that you could take to add a different play style to a class. Such kits required you to meet certain requirements to take them though. In the The Complete Wizard's Handbook, there was a Wizard kit called the Witch. In the description of the Witch kit, it is mentioned that most Witches are female, but male Witches are possible, being commonly referred to as Warlocks. The Witch kit states that the power the Witch gains, is taught to them by extraplanar entities, for a variety of reasons. In exchange for this magical knowledge though, Witches constantly had to struggle with the extraplanar entities to maintain their free will. Unlike traditional Wizards, a Witch needed to be more than just Intelligent, requiring decent Wisdom and Constitution scores as well. While this kit is not an official Warlock class, it was the first time the themes of the Warlock made it into a player class.

3.5

The 3.5 ed Warlock was introduced in Complete Arcane. It looks like textbook munchkin bait, but is actually kinda meh. Warlocks have at-will casting and no spells per day in 3.5, which made some people call hax but isn't so hot because very few DMs would ever run enough encounters in one in-game day for Vancian casters to completely run out of spells. Among the ones the handful that do, some like to have spells that are at-will and keep 3.5. One of the Warlock's most powerful abilities is to DAKKADAKKADAKKA with Eldritch Blasts, without having an accuracy problem. This ability can win encounters, but the time necessary to do so balances it out, so this class is both for people who want fast combat going The Matrix on the ceiling, and for patient masterminds.

Pathfinder

Pathfinder didn't give the warlock a conversion due to their non OGL status. Occult Adventures, however, introduced the Kineticist class, which follows Warlock mechanically a bit more closely than Magus to Duskblade, but thematically you are an element bender instead of having made vague deals with evil outsiders or fey. The witch takes up the flavor portion of the warlock while having its own mechanics.

Then Ultimate Intrigue came along and made warlock an archetype of the Vigilante. In this context, they are more Vigilante Arcane spellcasters. While they have some Magus spellcasting, they also can sling magical bolts, and still use almost all the vigilante tricks of misdirection, masked combat, and walking straight past the guards after making a quick change of outfits.

4e

When 4th edition rolled around, Warlocks made a surprising leap into the Player's Handbook, supplanting the Sorcerer as "the other PHB mage class". Classified as Arcane Strikers, Warlocks were flavored as eerie, sinister casters who could place victims under dread curses and gain magical benefits by reaping the souls of those they had cursed. They were also somewhat stealthy, thanks to their "Shadow Walk" feature, which granted them concealment until the end of their next turn on any turn in which they moved at least 3 squares. Like all classes in core 4e, the Warlock had subclasses, and a very obvious basis: their Pact, or what 5e would rename their Patron; the specific kind of unearthly entity that the warlock had received their power from, which even dictated one of their cantrips and also determined which kind of bonus they got from reaping the souls of those they had cursed. As a result, they started with three patron types in the PHB; the Fey, the Infernal, and the Star. In a step that 5e wouldn't replicate, a paragon level (11+) Warlock could take a feat called Twofold Pact, which represented them swearing allegiance to a second patron and getting access to its associated cantrip and pact boon, allowing them to choose which boon to benefit from whenever they d dropped a cursed enemy.

The Fey Pact was made with an Archfey or, really, any particularly strong fey. Fey spells tend to have themes of either "glamour magic" (seductive, intoxicating enchantments") or savage nature-type magic (such as setting a pack of ravenous sprites on a foe that rend the flesh from their bones). Their mandatory cantrip is Eyebite, and their pact boon is Misty Step (teleport 3 squares when a cursed creature drops to 0 HP).

The Infernal Pact was, as you can probably guess, made with a scheming devil, or maybe even one of the Archdevils. The least subtle of the pacts, it's all about scouring foes with fire, sucking away their souls, or invoking other hostile elements from Baator. Is mandatory spell is Hellish Rebuke and its pact boon is Dark One's Blessing (gain temporary HP equal to your level when a cursed creature drops to 0 HP).

The Star Pact is an odd one, with elements of the Cthulhu Mythos - basically, in the World Axis cosmology, certain stars are sapient and they're basically giant aberrations, which can bestow powers on those willing to risk communion with them. These stars were so new that they actually got an article in Dragon Magazine ("Wish Upon A Star", #366) that went full Lovecraft, detailing some of the most common of these "dark stars" and a Paragon Path, the Student of Caiphon, dedicated to one of these stars - something that would be followed up in Dragon #403's "Strange Constellations", which adapted Atropous, Father Llymic, Pandorym, Ragnorra and The Worm That Walks from 3e's Elder Evils into star-fiends that can empower warlocks. Arcane Power would present a far more benevolent motif for the Star-lock in the Master of Starry Skies PP, but overall they remain a creepy, creepy son of a bitch - and the only class in the PHB other than the Cleric that specializes in doing radiant damage! Their mandatory cantrip is Dire Radiance, and their pact boon is Fate of the Void (you gain a +1 bonus to one D20 roll of your choice made before the end of your next turn when a cursed creature drops to 0 HP - this bonus stacks, but it only remains usable for one turn).

For those curious, the "dark stars" named in that issue are Acamar, Caiphon, Delban, Gibbeth, Hadar, Ihbar, Khirad, Nihal, Ulban and Zhudun. These had actually first appeared as part of certain powers in the PHB1, alongside a never-detailed star called Thuban ("Tendrils of Thuban", a level 15 daily spell, which paralyzes and consumes a cluster of foes with tendrils of of liquid summoned from the frozen emerald seas that lie under the star Thuban). The Monster Manual 3 would create a sadly under-developed monster category called the Star Spawn; celestial aberrations representing the progeny of these terible stars, and even statting one such star - Allabar, Opener of the Way, a living planet corrupted by the Far Realm - as the most powerful of them.

When the Forgotten Realms Player's Guide rolled around for 4e, it introduced the new Dark Pact, an alliance made with horrible, malevolent spirits native to the Underdark and popular with drow warlocks, resulting in spells focused on darkness, poison, madness, and spite. Several of its iconic spells possess the ability to gain upgrades if you inflict damage on your allies, although even without this "augment" they're quite beefy. Its mandatory cantrip is Spiteful Glamor, and its surprisingly complex pact boon is Darkspiral Aura (when a cursed creature drops to 0 HP, your Darkspiral Aura value gains 1 point; you can use your Darkspiral Aura as an immediate interrupt when an enemy makes a melee or ranged attack against you, inflicting 1d6/1d8/1d10 Necrotic & Psychic Damage per point in your Darkspiral Aura; if this damage is less than 12, your Aura drops to 0 points; if more than 12 damage, you can halve the damage you take and your Aura drops to 1 point - you lose all Aura points when you take a short rest).

Dark Sun did the same thing; the Sorcerer-King's Pact was its attempt to recreate the Templar of AD&D, that strange pseudo-priestly class that derived its powers from its oath of allegiance to the tyrannical mage-psions of Athas' last cities. Its mandatory cantrip is Hand of Blight, and its pact boon is Fell Scorn - this strange feature is borrowing some elements from the psionics rules system, and can trip up an unobservant reader; the Sorcerer-King pacted Warlock has a single point of "Fell Might", which can be spent when casting certain spells in order to trigger some upgraded effects, and is recharged whenever the warlock drops a cursed creature to 0 HP. This trait is controversial to say the least because, normally, pact-associated spells don't need to spend this sort of resource to get their bonus. Even though Fell Might will recharge like crazy because, hey, cursing people is what a warlock is supposed to do, it still leaves a sour taste in the mouth.

Arcane Power would introduce what many wrongly believed to be the last of the Core pacts, in the form of the Vestige Pact; obviously themed after the Binder of last edition, the Vestige Pact calls upon the spirits of bizarre ghosts and ancient, forgotten entities, with a unique mechanic attached to it. Each Daily power associated with this pact, always named "Vestige of whoever", becomes a Vestige in the Warlock's arsenal. Whenever the warlock completes a rest, they can determine which Vestige is their "Active" Vestige - they can also choose to change their Active Vestige whenever they use one of those Vestige powers, causing the newly invoked Vestige to become Active. Your Active Vestige determines the effects of your pact boon and the secondary effects of your mandatory cantrip, "Eyes of the Vestige".

The reason that neither Vestige nor Sorcerer-King was the last of the Core 4e Warlock Pacts? Hidden in the Essentials era sourcebook "Heroes of the Elemental Chaos" is the Elemental Pact for core warlocks. Representing the obvious choice of a warlock drawing their power from a Primordial, this elementalist warlock has some slight overlap with the Wild Mage, but not much. It gains the bonus feature "Elemental Affinity", where you have Affinity to either Acid, Cold, Fire, Fire, Lightning or Thunder - this is determined randomly each time you complete a rest, and you can change your Elemental Affinity when you invoke your second wind. When you cast an arcane attack power that deals Force, Necrotic, Poison or Psychic damage, you can make it inflict whichever damage type you have Elemental Affinity for instead. Its pact boon is Accursed Affinity; after you drop at least one cursed victim, everyone you place your Curse on for the rest of the encounter gains Vulnerability (5/tier) to whichever damage type you currently have Elemental Affinity with.

Essentials also introduced two Warlock Variant Classes (alternatively known as subclasses); "Heroes of the Forgotten Kingdoms" introduced the Hexblade, an Arcane Striker-Defender that is basically a cross between a Warlock and a Swordmage, whilst "Heroes of Shadow" introduced the Binder, a restyling of the Warlock into a full-fledged Arcane Controller.

The Hexblade was initially introduced with only Fey and Infernal Pact options; it gained its own version of the Star Pact in Dragon #393, an Elemental Pact in "Heroes of the Elemental Chaos", and a Gloom Pact in "Heroes of Shadow".

The Binder, as the very last Warlock derivative to emerge prior to 4e's cancellation, only had the two Pacts; Gloom and Star, both in its native "Heroes of Shadow". It did manage to gain a Fey Pact for itself in Dragon #406.

It bears mentioning that, whilst original/"Core style" warlocks can take the spells from both the Binder and the Hexblade for themselves, the "Pacts" as used by these variant classes are not synonymous with the Core-lock's Pacts, so Gloom Pact spells have no special riders when used by non-Binders or Hexblades. This is one of the many reasons why most of 4e's fans didn't like the "simplified" versions of classes created for Essentials.

4e paired the Warlock class up with the Tiefling race, much like how Dwarves make iconic Fighters or Clerics, or Elves make good Wizards, or Half-orcs make good Barbarians. 5e continues this tradition.

4e Sample Patrons

Issue #381 of Dragon Magazine featured an article called "Performing the Pact", which provided some example Patrons for each of the five pacts available at the time.

The Dark Pact patron is Yorgrix, Weaver of the Poison Web: once a demonweb spider kept as a familiar by an overconfident drow matron, Yorgrix patiently mastered the dark magic it watched its mistress perform and then, fueled by hunger and ambition, slew and devoured both her and the entire city in which she dwelled. Glutted on countless souls, Yorgrix was transformed into a dread spirit; now imprisoned in the city it massacred, it reaches out to the minds of mortals with a simple promise: power for food.

The Fey Pact patron is The Eochaid, a strange fey spirit embodying the interplay between nature and arcane magic, and which manifests as a strange amalgamation of humanoid, animal and plant. Ancient as the Seldarine themselves, the Eochaid desires only to promote and strengthen magic, seeking its growth. Those willing to plant magic's seed - and to retrieve arcane artifacts for it to protect - are blessed with its wild hexes and unearthly glamors.

The Infernal Pact patron is The Prisoner in Iron, an infernal warlock of such power that the Archdevils feared him and have bound him in the deepest dungeons of Dis, hoping to hide him forever. But such is his power that he can still reach out to the mortal world, offering tutelage to the ambitious, seeking to empower a champion mighty enough to free him from his chains.

The Star Pact patron is Ulban, the Wanderer; a sapient time-traveling comet from a far-flung apocalypse, the last survivor of its universe. Now it wanders space and time, empowering those who, in some inscrutable way, will play their part in prevent Ulban's future from coming to be - often battling against the other dark stars in the process.

The Vestige Pact patron is The Bleak Guide, a reaper-like entity from the Shadowfell charged with maintaining the orderly transition of life to death, and more than willing to act as a go-between for vestiges and those mortals who will use their power to make is own existence easier. It can't act against the necromancers and undead that vex it so - but its mortal agents, on the other hand...

5e

The 5e Warlock is a complicated marriage of 3e invocations, 4e pacts, and 5e spellcasting, with a few caveats. They gain a pitiful amount of spell slots, as well as only a handful of spells known. To the untrained player's eye, they're painfully limited compared to "real" casters, but in reality they're roid-pumping nightmares not bad. Their spell slots all automatically scale the slot level up so their spells are always guaranteed to be pumped up, and also refresh after every encounter or few (short rest). Invocations are back from 3.5, albeit scaled back a bit, providing various kinds of special abilities, from access to spells that aren't on their list as at-will, encounter or daily powers, to power-ups for the pact form, and of course power-ups for Eldritch Blast.

To complete the Warlock package, you get a pact with a supernatural being. The pact gives you a thematic extended spell list; for example, Great Old One Warlocks can cast (but not spam, sadly) Evard's Black Tentacles. Pacts provide a bevvy of unique class features like teleportation, damage resistance or telepathy. On top of magical powers, they also give you a consolation prize in the form of a pact boon, which can either be a souped-up familiar, a free enchanted weapon that you can shapeshift into whatever kind of weapon you need, or a magical book that gives you three cantrips from any other spellcasting class. An alternative pact boon was the Star Chain, introduced in "Non Divine Faithful", which closely ties into the Seeker patron: this is a magical trinket that can be used to cast Augury and can be used to grant Advantage on an Int check once per short rest.

The available pacts are:

Archfey - Bound to a powerful faerie lord or sylvan pseudo-deity, a warlock with this pact gains the power of Fey Presence (Charm or Frighten all creatures in a 10ft cube around you once per short rest), Misty Escape (teleport 60 feet and turn invisible once per short rest), Beguiling Defenses (you are immune to Charming and can attempt to Charm anyone foolish enough to try a Charm effect on you) and Dark Delirium (can attempt to entrap a target in an illusion to Charm or Terrify it once per short rest). This one is in the Player's Handbook.

Fiend - Bound to a Demon Prince or Archdevil, a warlock with this pact gains Dark One's Blessing (gain temporary HP for dropping another creature to zero HP), Dark One's Luck (can choose to re-roll an ability check or saving throw with a +10 bonus once per short rest), Fiendish Resilience (gain Resistance to a single damage type of your choice after completing a short rest, though magic and silvered weapons can pierce it) and Hurl Through Hell (teleport a target into some hellish dimension for 1 turn, causing 10D10 Psychic damage to a non-fiendish target, once per long rest). This one is in the Player's Handbook.

Great Old One - Warlocks with this pact are bound to terrible abominations from outside time and space, drawing on the power of aberrant gods like Cthulhu. They gain the boons of Awakened Mind (telepathy with a 30ft range), Entropic Ward (can make yourself harder to hit and get a bonus if the target missed once per short rest), Thought Shield (mind cannot be involuntarily read, Resistance to Psychic Damage, inflict equal Psychic damage on anyone who inflicts Psychic damage on you) and Create Thrall (permanently charm a single creature with a touch, gaining telepathic communication with them from anywhere on the same plane). This one is in the Player's Handbook.

Undying - A Warlock with this pact has offered their soul to something that has "cheated death"; most obviously a powerful lich, ghost or vampire, but mortals ascended to godhood and weirder things are also valid. The Nameless One isn't mentioned, but would be a perfectly thematic (and awesome!) patron for this pact. The "necromantic" pact, these warlocks get features related to the ability to cheat death; Among the Dead (Spare the Dying as a bonus cantrip, Advantage on saving throws against disease, Undead must pass a Wisdom save to attack you), Defy Death (gain a significant healing 1/day by passing a death saving throw or using Spare the Dying), Undying Nature (can hold your breath indefinitely, don't need food, water or sleep, immunity to magical aging, age 1 year for every 10 you live) and Indestructible Life (can freely heal yourself 1/encounter, including reattaching limbs as part of it). Comes from the Sword Coast Adventurer's Guide.

Hexblade - Basically, you want to play a character inspired by Elric of Melnibone; your power is with a mysterious Shadowfell entity that makes its presence felt through powerful weapons bound with shadowy magic. Despite this, you don't have to take the Pact of the Blade. Having first appeared in Unearthed Arcana, the official version came out in "Xanathar's Guide", at which point it seems to have absorbed some of the fluff, if not the crunch, from the Raven Queen patron featured in that same UA. This pledge makes the warlock more of a melee combatant, in the vein of the class it takes its name from; their two level 1 features are Hexblade's Curse (1/short rest, place a curse on a foe within 30ft that makes your attacks more likely to hit and heals you if they die whilst cursed) and Hex Warrior (you can enchant one-handed weapons you are proficient with to use Charisma for their attack & damage rolls; if you've the Pact of the Blade, your Pact Weapon always has this trait no matter the form it takes, also you get free proficiency with medium armor, shields and martial weapons). At level 6, they gain Accursed Specter (raise a slain humanoid as a loyal specter 1/day). Their level 10 feature, Armor of Hexes, buffs up their curse by letting the warlock negate a cursed opponent's attack against them on a 4+. Finally, at level 14, they get Master of Hexes, which lets them forgo the healing effect for dropping a cursed opponent to instead immediately reapply that curse to a fresh opponent. Its bonus spells are close-ranged, a mixture of protective spells (shield, blur, blink) and temporary weapon enchantments - the only exceptions are Phantasmal Killer and Cone of Cold.

Celestial - This is the "good guy warlock" patron option, where you make a pact with an angel of some description. In mechanics, it's a refluffed version of the Undying Light Patron presented in an earlier Unearthed Arcana - ironically, unlike the Hexblade, this version was so well-received that WoTC saw no need to change its subclass features when they reprinted it for the Xanathar's Guide to Everything. The difference between the two versions is that it adds some healing spells to its list of bonus spells, instead of just fire/radiant damage-dealers, and rearranges what levels you get which features at. At 1st level, you gain Healing Light - the "heal with a touch" feature from the UL Patron, which it didn't get until level 14 - and Light & Sacred Flame as bonus cantrips. At level 6 it gets Radiant Soul, which is Resistance (Radiance) and bonus to radiant & fire damage, a feature the UL got at 1st level. They both get the same "bonus temporary HP on completing a rest" feature at level 10, but the Celestial renames it the Celestial Resilience trait. Finally, it gets Searing Vengeance - 1/day, when reduced to death, spring up at half maximum hitpoints and inflict radiant damage & blindness on all enemies within 30 feet - as its 14th level trait, when for the UL Patron it was a 6th level feature.

A minor footnote on D&D 4e and 5e Warlocks

One of the roleplaying possibilities for Warlocks that sometimes gets mentioned is that once empowered, the Warlock is under no obligation to keep obeying their Patron. The rules explicitly do not contain any references to any of the patrons being able to strip the powers from a Warlock, unlike, say, a Paladin--in other words, the implication is that once granted, a Warlock's powers are theirs to keep. (It's mildly worth mentioning that "Warlock" decends from the old English "wǣrloga", meaning "traitor or deceiver" ("wǣr", meaning "covenant, truce, or pact" and "loga", meaning "liar"), and that kind of name cuts both ways.)

This was intentional (as, among other things, it allowed for Lawful Good Infernal Warlocks), and influenced the initial three 4e Patron choices (and a few later ones): Who would give away free power to mortals that you could not revoke? Somebody whose cause is advanced by the mere usage of that power; Devils, Archfey and The Great Old Ones all obviously qualify (as did Vestiges)--all were (in 4e's default cosmology, at least) restrained in some way from the mortal world, and higher level 4e Warlock powers, at least, frequently gave them some temporary purchase on said world when used.

(Here's a Mike Mearls interview that explicitly notes this possibility in 5e, as well. Then again, Mearls also implies in that interview that Clerics can turn against their Deity and still have their Divine Magic, so take that claim for what it's worth. Admittedly, Divine classes did lose their "powers are revoked if your deity is pissed" trait in 4e, so it's not unprecedented.)

DMs should also note that while the Patron cannot directly withdraw the Warlock's new powers, they are also not restricted from sending repo men to get the recalcitrant Warlock back in line if the Warlock still has debt outstanding.

The Classes of Pathfinder 1st Edition
Core Classes:	Barbarian - Bard - Cleric - Druid - Fighter - Monk Paladin - Ranger - Rogue - Sorcerer - Wizard
Advanced Player's Guide:	Alchemist - Antipaladin - Cavalier Inquisitor - Oracle - Summoner - Witch
Advanced Class Guide:	Arcanist - Bloodrager - Brawler - Hunter - Investigator Shaman - Skald - Slayer - Swashbuckler - Warpriest
Occult Adventures:	Kineticist - Medium - Mesmerist Occultist - Psychic - Spiritualist
Ultimate X:	Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante