The warlock debuted in 3rd Edition Dungeons & Dragons as an arcane spellcaster with unlimited magic. Well, unlimited as in you could use it whenever you wanted: you only started the game with the ability to make a magical ranged attack and one other thing (like creating fog clouds or spiderclimbing on walls).
3rd Edition's warlock didn't really mention pacts. The closest it gets is a line about how "a few blameless individuals are simply marked out by the supernatural forces as conduits and tools". Otherwise like sorcerers they can be born with their powers, but instead of the magic being in their blood its described as being part of their soul.
4th Edition's warlock has you choose a type of pact, though only the Fey Pact mentions forging an actual bargain: the Infernal and Star Pacts make it sound like you just learned your magic like a wizard learns his spells. It follows the standard At-will/Encounter/Daily power model that most other classes do, differentiating itself from other spellcasters by being able to curse enemies (bonus damage plus a minor benefit if you kill a cursed enemy).
While you can choose almost any spells you want, many give you an additional kicker effect if you have a specific pact, thereby encouraging you to stick with the more thematic options.
5th Edition's warlock mentions both pacts and patrons. As with 4th Edition you choose a pact (albeit at 3rd-level instead of 1st for some reason), which grants a benefit such as a familiar or the ability to summon a magical weapon. The class is otherwise a mix of pseudo-Vancian magic, plus some at-will and encounter spells. So, basically like 4th Edition, except you don't automatically start with eldritch blast and some sort of damage-boosting curse ability.
Really the only thing I liked about the 5th Edition warlock was that it at least suggests figuring out how big a role your patron plays in the campaign and your relationship with it, something that was lacking at least at the start of 4th Edition.
When developing the warlock for A Sundered World I kept 4th Edition's pacts, but created a debt mechanic to ensure that your patron's influence and desires could never be overlooked or forgotten. I also added a move so that you could get in touch with your patron and to see if it had any jobs on hand: taking the initiative to see what it wants instead of waiting for a call gives you some extra benefits.
Unlike every other Dungeon World spellcaster I've seen (and created), when a warlock casts a spell it always works: you pick what you want to do from a list, it happens, and then you make a Charisma roll to see how much debt you accrue. When your debt gets high enough it resets to 0 and your patron gives you a job: until you get the job done you take a constant penalty to further uses of warlock magic, and if you get too many jobs the GM can decide that your patron pulls your magical plug until you get shit done.
I want to do something similar with the warlock for Dungeons & Delvers: Black Book.
As with the version from A Sundered World you'll choose a type of patron. Right now I'm thinking that there will be general warlock talents, plus talents specific to a pact type, so if you choose the Star Pact you can summon eldritch horrors but not demons, and the Fae Pact won't let you immolate your foes with blasts of hellfire. Something like winged flight I think is general enough for any of them, though.
You'll also start with eldritch blast automatically, which will be raw, unshaped magical energy, basically a ranged Charisma attack similar enough to the wizard's Magic Missile. I'm thinking about having the Pact type alter this, so Infernal Pact makes it inflict fire damage, Fae Pact can have it inflict radiant or cold damage (depends on if you go summer or winter fae), and Star Pact makes it deal psychic damage.
I actually worked on a homebrew warlock class for 5th Edition back when I thought it might result in a game I'd enjoy (I later made a new pact when they got around to making an "official" warlock). One of the class features I included (and for a short while was part of the official version) was simply called sign, and had you gradually physically transform over time.
As before the sign will start out small, something that can be easily concealed, but as you gain more warlock levels you'll continue changing until there's just no hiding it. Like, for the Star Pact you might have an eye or mouth somewhere on your body, and as you level up you'll start growing tentacles, more eyes and mouths, and so on until you look like the alienist from Tome & Blood.
As for other spells, I'm thinking of giving you one spell that you can use at-will, no problem, and you can speak to your patron (10 minute ritual) to swap it out for something else. Higher levels let you have more at-will-no-cost magic on tap, though I'm not sure if I want to have them automatically scale, or let you "rank up" by using multiple I guess "slots" on the same ability.
So at 1st-level you could temporarily bind a creature in chains, and then at 4th- or maybe 5th-level you could choose a second ability, or rank up binding chains to make it deal more damage and also restrain or something. Since you can hit up your patron to swap them around, you can experiment without worrying about having a (mostly?) useless ability.
Another way to differentiate them from other spellcasters is that they won't have an automatically replenishing spellcasting resource like Mana or Favor. Instead they'll have Boon, which they can only earn it by doing or giving things to their patron (have to put in guidelines for how much to give for doing things, but for trading stuff I'm thinking 50 sp per Boon since clerics can sacrifice 50 sp worth of stuff for 1 Favor).
Depends on how much bang you can get per Boon.
Current uses for Boon includes casting more potent spells (that can only be cast by spending Boons), maybe bonuses on various d20 checks and saving throws, and boosting your at-will stuff. Really the trick is making sure its worth the effort, but not making it too good. Ah, well, that's what playtesting is for.
So, what do you think? Does this class sound interesting to you? Better than current warlocks on the market? Is there something other warlocks can do that you'd like to see this one do? Once I hammer out a five-level version it'll be part of the next Appendix D issue (probably along with racial classes).
Dwarven Vault is our sixth 10+ Treasures volume. If you're interested in thirty dwarven magic items (including an eye that lets you shoot lasers) and nearly a dozen new bits of dungeon gear, check it out!
Just released our second adventure for A Sundered World, The Golden Spiral. If a snail-themed dungeon crawl is your oddly-specific thing, check it out!
By fan demand, we've mashed all of our 10+ Treasure volumes into one big magic item book, making it cheaper and more convenient to buy in print (which you can now do).