How to build a warlock: the caster who signed for it

A warlock's origin story is a transaction, and transactions have two sides. Somewhere there is a ledger with your character's name in it, and the being holding the pen has plans. That is the class's gift to a campaign: where a wizard's backstory is a syllabus and a sorcerer's is an accident, a warlock's is an unresolved relationship with something that can collect. Loreweaver's warlocks answer to The Fiend, which sharpens the question deliciously: whatever your character bought, a devil believed the price was worth paying.

The strong concepts start with the moment of the deal. A midwife who whispered yes over a dying newborn and has never told the mother what the child now owes. A ruined merchant who signed to save the family name and discovered the name was exactly what he sold. A soldier who called out to anything listening under the walls of a burning city, and something under the city answered. The pact does not make these people evil; it makes them leveraged, which is more interesting.

In play, the warlock is a Charisma caster with a working-class engine: light armour, a d8 hit die, and Eldritch Blast (the class's own cantrip and the most reliable damage beam in the game) doing the every-round work so the real spells can wait for the moment that deserves them.

Your patron arrives at level 1, because the deal is the origin, not a milestone. The Fiend's opening gift is Dark One's Blessing: every time you drop a hostile creature to zero, you pocket temporary hit points equal to your Charisma modifier plus your warlock level. Read the incentive: the devil pays out on kills, so position yourself to land the last hit. The patron also slips extra fire-and-brimstone options onto your spell menu as you level, Burning Hands and Command first, with Scorching Ray and eventually Fireball waiting further in.

Before any of that matters, understand Pact Magic, because it is not the casting system every other guide taught you. You get very few slots: one at level 1, two from level 2, and that pair is what you own for most of your career. In exchange, two things: every slot is always your highest available level (they climb to second-level at class level 3 and third at 5, no low-level dregs to track), and they all come back on a short rest. A wizard budgets slots across a day; a warlock budgets across the next fight and asks the party for an hour's rest afterward. Same word, entirely different game.

Level 2 opens Eldritch Invocations, two picks from a long menu of standing bargains: Agonizing Blast adds your Charisma modifier to every Eldritch Blast beam and is close to mandatory for blasters, Devil's Sight sees through magical darkness out to 120 feet, Mask of Many Faces casts Disguise Self at will, forever, free. You will hold five invocations by level 9 and can swap one at every level-up, so nothing here is a life sentence. Level 3 is the Pact Boon: Blade summons a weapon you are proficient with, Chain upgrades Find Familiar into an imp or sprite, Tome adds three cantrips from any class's list. Level 4 is the standard first Ability Score Improvement into Charisma, and level 5 raises the pact slots to third level and unlocks the invocation tier where Thirsting Blade gives Pact of the Blade its second attack.

The storm-signer. A half-elf Sailor whose ship went down in a gale everyone else remembers as unsurvivable; she remembers the voice in the water and the exact wording of what she said back. Half-elf's +2 Charisma and two floating +1s (Constitution and Dexterity) build the classic blaster chassis; Athletics and Perception from the Sailor keep her useful on any deck. Pact of the Chain at 3 puts an imp in the rigging as a scout, and the pairing every fiendish warlock eventually discovers (Devil's Sight plus the Darkness spell) turns a black cloud into a private hunting ground only she can see through.

The debt inheritor. A tiefling Criminal who did not sign anything; a grandparent did, and the contract turned out to be heritable. Tieflings arrive fiend-flavoured already: +2 Charisma, fire resistance, and the Infernal Legacy cantrip line running in the blood. Pact of the Tome at 3 suits a character whose whole life is other people's paperwork, and Mask of Many Faces makes her the party's infiltrator: a new face at will, every day, no slot spent. Her Deception proficiency isn't a skill, it's an upbringing.

The last man on the wall. A human Soldier who made his bargain audibly, mid-siege, and walked out of a breach that killed his whole company. Human +1s across the board support a front-half build: Pact of the Blade at 3, Thirsting Blade at 5 for the second attack, Fiendish Vigor for the standing false-life buffer. Dark One's Blessing is his rhythm section: every enemy he finishes hands him temporary hit points, and a blade-lock lives and dies on that trickle. He fights up close because the day he made the deal, that's where he was standing.

The first trap is hoarding slots like a wizard. If your two slots are still unspent at the end of an adventuring day, you played most of it as a cantrip turret for nothing. Pact Magic refills on a short rest; the discipline is spend, rest, repeat, and it includes the social move of actually asking the table for short rests. A party that never stops for an hour is quietly taxing its warlock, and you're allowed to say so in character.

The second is buying damage spells with your tiny spells-known budget. You know two spells at level 1 and roughly one more per level after, while Eldritch Blast with Agonizing Blast already outperforms most levelled blasts you could buy, every round, for free. Spend the known slots on things a cantrip cannot do: Hold Person, Suggestion, Misty Step, Counterspell. The devil gave you a gun; buy levers.

The third is going blade-side without respecting the chassis. Pact of the Blade grants a summoned weapon and proficiency; it does not grant heavy armour, extra hit points, or the second attack, which waits for Thirsting Blade at level 5. A level 3 blade-lock in light armour who charges the front line is a d8 caster cosplaying a fighter. Until 5, treat the blade as a sidearm and Dark One's Blessing as your body armour: finish wounded enemies, bank the temporary hit points, stay near the exit.

The Fiend's ledger keeps paying interest. Dark One's Own Luck at 6 lets you add a d10 to a check or save once per rest after you see the roll: the devil nudging dice it has money on. Fiendish Resilience at 10 lets you pick a damage resistance at every rest and re-pick it like a wardrobe. From 11, Mystic Arcanum rebuilds your top end: one 6th-level spell castable once per long rest without a slot, then a 7th at 13, an 8th at 15, a 9th at 17, so the pact's ceiling keeps rising even though the slots themselves plateau at 5th level from class level 9. Hurl Through Hell at 14 is the patron showing off: hit a creature and mail it through the lower planes for a round, and if it isn't a fiend it returns carrying 10d10 psychic damage worth of the scenery. At 20, Eldritch Master lets you spend one minute entreating your patron to refill every pact slot once per long rest, which is, fittingly, the only feature in the class that requires you to ask.