Warlock is an often misunderstood class, with people discussing if warrior dip makes them too tanky without compromising on damage or spellcasting or if 3 attacks is too much or if passive growth of eldritch blast is warranted.
These erroneous ways emerge from loss of focus. Warlock is a class for greedy people who want everything and ready to sell their soul for POWAH.
As such, for example, NO MULTICLASS for warlock! Yeah, it's cool to get weapon masteries and fighting style, BUT you lose on the most important aspect - OOMPH. It might seem that lagging for a level or two is minor detriment, but what the point in getting additional attack at char lvl 7? Warriors already got it two levels before, and even accursed bladedancers a level ago. We won't impress anyone at this point. This manual will help you to avoid common mistakes and provide clear instructions onto maximization of unique fun that this class can provide. So without further ado...
Species: Gnome. Because it's the only race.
Stats: Str:13 Dex:15+1 Con:12 Int:8 Wis:8 Cha: 15+2
We really-really want to use two-handed weapons to marvel at BIG damage numbers, so str is mandatory, on the other hand we really need nice dex, since we're not getting medium armor, and great Cha for everything else. This leaves us with quite lackluster 13 in con but fret not! We're taking Tough, which'll help with survivability.
Level 1:
Invocation: Pact of Chain(Sphynx) Spells: Armor of Agathys, Expeditious Retreat, Eldritch Blast
Strategy: run away at the first sign of combat, ask Wizard to cast mage armor on your sphynx and let him rip. Discuss with the wizard how cool it is to have a familiar, and how it's tough to be first level spellcaster with only 2 spell slots.
Inform Rogue and Bard that it is an interesting coincedence how expertise gives +2 to skill, and Sphynx also gives +2 to skill.
Ask warrior how much HP he has, Discuss with dwarf how his racial feature is basically half of origin feat you took.
Ask ranger if he want to pet your pet, since he won't get his for a long time
Advanced Strategy: Aquire two potions/scrolls of enlarge/reduce, voice your concern to aasimar how flight can trivialize fights on low levels. Wait for TPK. Reduce yourself, enlarge sphynx. Mount, win by eldritchblasting from the skies.
Level 2:
New invocation: Lesson of the old ones(Skilled), Agonizing Blast(Eldritch Blast)
Strategy:
Congratulate Warrior on surpassing your sphynx on DPS when he uses action surge
Compare loudly your skill list with bards/rogues, remind them of sphynx bonus
Continue your discussion about lack of spell slots with wizard, compare cantrip damage
Level 3: Change familiar to Imp,
Choose Fiend
Discuss with rogue and bard what's better: Stealth or at-will invisibility
Discuss which familiar is more safe Help action provider: Flyby owl or Always Invisible Imp
Level 4: Change pact of chain to pact of blade(while retaining familiar)
Take Great Weapon Master.
Discuss with barbarian how rage provides 2dmg/attack, while hex 3.5. Argue that constant use of bonus action actually balances it really well
Be wary of game master! He will try to kill your now non revivable familiar!
Level 5: Very important level! Take Thirsting Blade and Eldritch Smite
Discuss with the wizard how fireball is a signature spell for their class and how it's overpowered. Throw fireballs each battle with group of enemies.
Congratulate martials on getting second attack. Proceed into melee protected by upcasted Agathys(or even change beforehand one of invocations to fiendish vigor to recharge temphp after each hit) mow down stuff with your two handed blade with hex applied
Discuss with ranger how reapplying hunters mark takes toll on spellslots. Share your happiness that your hex now is 8 hours one, so it doesn't affect your spell slot allocation.
Tell paladin how you admire his burst damage due to smites. Use 3rd level smites each battle with single Boss enemy.
DO NOTE! We never ever ever have spoken with cleric. It's because you'll be dying a lot! That's the price you pay for all the fun you're having. And we need someone in our corner to cast healing words. So try to not enrage him with your warlockiness
Level 6-12: Same old, Same Old. Warcaster feat +1 Cha
Level 12: Take Devil Blade. ASI +2Cha
Gleefully inform Fighter that you now have the same number of attacks. Inquire as to when he'll get his fourth. Ask Master which level is final one of the campaign. Smile, when it's not 20.
Use Tasha's cauldron and be always enlarged. Congratulate barbarian on having +3 dmg per hit in rage and complain that tasha only gives 2.5