Well, Adventurer, I’m glad you asked.
In 5th Edition, my favorite class is, hands down, the warlock. When I first picked up the book, I expected it to be bard. Bards were my favorite class in 4E; I liked the notion of warlocks, but in 4E they were pigeonholed into the “striker” role (high damage to single targets) to a greater degree than interested me.
In 5th Edition, the warlock class has great options for supporting that style of play, to please their fans returning from 4th edition (this was one of the design goals for 5E). Many people are so taken by the combination of the spell hex, the cantrip eldritch blast, and the invocation Agonizing Blast that they declare they are “core features of the warlock” and necessary and expected rather than optional.
This is far from true, but it is true that taking these three options in your first two levels will do a lot to give you what you’re missing if you were a 4E warlock. It’s also true that taking these three options–which represent a fraction of your overall character-building decisions—frees you up to do basically whatever else you want with the rest of your spell and invocation selections and always know that your character will be one of the most consistently effective combatants in the party. You can pick all your other abilities based on what sounds fun or what fits your character or what has the most pleasing pattern of white space around it, and you’ll be fine.
I don’t always go for that combo myself, but if you’re considering playing a warlock it’s good to know about it for that reason.
The fact is, warlocks in 5E have a lot of things going for them. First, there’s what people call the “fluff”… the backstory, the exposition, the roleplaying cues and plot hooks. You do magic, okay? But you don’t know magic like a wizard is, nor are you magic in the way that a sorcerer is. Instead, you sort of have magic… but if the cops ask, it’s not yours. You’re just holding it for a friend.
Maybe you made a classic deal with a devil. Maybe you are sworn to the service of a fey monarch. Maybe you read a forbidden tome full of unspeakable secrets and something in it broke through the feeble shell of your workaday mind and put you in contact with something vast and implacable and unfathomable, somewhere out there in the darkness between the stars…
Mechanically, warlocks are weird. My boyfriend was just brushing up on the multiclassing rules and was surprised to learn that warlocks aren’t included in the MC spell table. “No,” I told him. “Warlocks are the weird loners sitting off in the corner talking to their invisible friends.”
Where every other spellcasting class has a feature called “Spellcasting”, warlocks have one called “Pact Magic”. While every class’s Spellcasting feature is slightly different, the warlock’s Pact Magic is completely different, hence the name.
Warlocks don’t have one set of slots for each level; they have one set of slots, which grow in power (level) as they do. Warlocks don’t get their slots back on a long rest, but on a short one. And where most dedicated spellcasters have spell slots that go up to 9th level, the Warlock’s weird quick-refresh slots top off at 5th level. A level 20 Warlock has only four spell slots at a time, but they are all 5th level, and they come back on a short rest. If you rest twice a day, that’s 12 5th level slots.
Of course, that’s only part of the story. Warlocks also get invocations, which are like mini-feats that represent eldritch secrets they glean from their patrons. Some of these just boost eldritch blast. Others give you supernatural powers that aren’t otherwise accessible. And some of my favorite ones give you access to spells that aren’t on the warlock list, some on an unlimited basis. Even at level 2, warlocks with the right invocations can cast spells like disguise self and speak with animals as if they were cantrips.
And while warlocks never get slots above 5th level, their spell list goes up to 9. Weird, huh? That’s because they get a class feature called “Mystic Arcanum” at certain levels that gives them one spell of each level 6th through 9th, which doesn’t use a slot but can be cast once per day.
Mechanically, the reason for these weird invocations and arcana instead of just having all those spells as, well, spells, is that it makes it easier to balance a class that has few spell slots but always gets them back. If a warlock’s slots progressed all the way to level 9, they could be casting four level 9 spells in a row, resting, and then doing it again. Barring some truly epic level stuff, no one else can cast two level 9 spells in a day, much less four or eight or twelve.
At the same time, all the little utility spells that show up as invocations would rarely be justifiable “expenditures” when you’ve only got a maximum of two slots at a time for so much of your career.
But the upshot of the way all of these things work—spells, invocations, and mystic arcana—is that warlocks play much less like a standard mage and more like someone who just has magical superpowers.
All that said, while warlock is my favorite class, I will say that you can’t go wrong with any class in 5E. They’re all exceptionally well-designed. I would never have imagined myself playing a paladin or a fighter, for instance, but I’m playing one of each right now.
If you do go warlock yourself, a piece of advice: make sure the rest of the party knows how short rests work and that they are important to your character, and make sure your DM is not a “short rest non-believer” (there are a dismaying number of those).
The short rest is built into the balance of 5th Edition. Without it, some characters (notably monks, warlocks, and to an extent fighters; to a greater extent, Battle Master fighters) are hampered in comparison to others. You should be trying to take a short rest after every two fights or so. If your party balks at this, try reminding them that short rests allows them to spend hit dice, which allows the cleric or whoever to save spell slots for things other than healing.
If they still balk, rather than hoarding your precious few spell slots, use them for something awesome and then tell the party, “Did you like that? Okay. The price is that our characters take a lunch break so I can keep being a warlock in the afternoon.”
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