I cannot fathom, for the life of me, what Warlocks are for, or how to use them. I couldn't figure them out in NWN2, or in 3.5 to begin with, and I still just don't get them. What do they do?
Wyll is.. kind of sucky as a Wizard, kind of sucky as an archer, kind of sucky as a melee combatant. I must be doing it wrong, what is it?
Warlocks are a bit nerfed currently in BG3, because of the unlimited Long Rests, and limited Short Rests. Things that makes warlock interesting:
Eldritch Blast This is the best damage cantrip in DnD 5s, and only available to Warlocks.
Not only is the base damage on this cantrip very high, Warlocks get the ability to improve it with Eldritch Invocations.
You can pick two Invocations on lvl 2. My personal favorites are Agonizing blast and Repelling Blast. Giving your Eldritch blast a +CHA modifier to your damage roll, and you get a 10ft push back on the blast.
This honestly is your main source of damage through the game.
Spell SlotsWarlock has a very different spell system to that of Wizards and Sorcerers. Like the Sorcerer you pick your known spells on level up, but all your spells are always cast on your highest spell level.
Warlock also get's their spell slots back on a short rest, unlike other spell casters. As a balance you tend to have very few spell slots. This is why I say Warlock is nerfed in BG3, since all classes have this feature with how long rests have no limiting factors, but short rest is only once per long rest.
HexHex is a core spell for Warlocks, it adds 1d6 necrotic damage to all your damage rolls. This is a concentration spell that in 5e lasts 8 hours, and in BG3 lasts until your long rest. You can keep casting it as long as you maintain concentration as a bonus action. It works very well with spells like Scorching Ray, which does three attacks.
Your spell slots is usually best used to get Hex up and running, and then on either utility spells, or comboing Hex with a multiple damage roll spell like Scorching Ray.
PactIt doesn't seem like these are fully implemented yet. I have usually gone Packt of the Chain which gives you access to find familiar, with an expanded list of familiars only available to Warlocks
Other Worldly PatronThis is more or less your sub class, and gives you an interesting expanded spell list, as well as some other features. Doesn't seem to be fully implemented yet
Armor Proficiency The Warlock is also proficient with light armor. Which is better than the Wizard's "nothing". Now one of the Invocations you can take is a once per long rest Mage Armor, if you so please, which is a good alternative to wearing light armor. But keep in mind that once you have Studded Leather +1 you no longer really need the mage armor, so I prefer to go with Repelling Blast. Especially in BG3 Early access where you can get Studded leather armor pretty early.
One Ability focusThe only ability you really want to max out is Charisma. This is because of Agonizing Blast. Having 20 in charisma means +5 on each of your Eldritch Blast damage rolls.
Beyond that you watn high Constitution to pass more concentration checks to maintain Hex, and dexterity to get a higher AC together with your Light Armor.
I find the Warlock to be a fun class in BG3, mostly because repelling blast has a lot of synergy with the mulit leveled design of the game, and feels really impactful when used.