Or maybe "why should I play as a Warlock"? I mean beyond the roleplaying possibilities of having bargained with an extraplanar entity, what makes it good enough to be picked among arcane spell casters? What are the game development possibilities? Or what mechanics makes it useful for this or that situation?

Because it seems tempting but the idea of learning less spells and having just a few spell slots available, still doesn't convince me. I like spell casters, that's why I play fantasy games, because I love Magic. But I still don't get it what could make a Warlock a suitable option for me. Maybe, based on your experience, you could advise me on the matter.

Part of the warlock 'kit' that makes them a potent player is for one, having access to the Edritch invocations, some of which are unlimited use.  Warlocks also have one of the most potent Cantrip spells with theirEldritch blast.  One of the reasons for its potency it does damage similar to a ranged longsword attack, with additional attacks at higher levels, allowing the warlock to make potent cantrip attacks.  The eldritch blast can be further upgraded with certain Eldritch invocations to further improve its potency knocking back, adding charisma to the damage among other.  

Though they don't have many spells, they do all regenerate with just a short rest.  

if you did go with a warlock, do you think would would take the Blade, the Tome, or the Chain?  (weapon, ritual casting, familiar)

Taking the Tome option gives you some extra spells you can cast an unlimited number per day (even though they take 10+ minutes to cast) which can be great for identify type spells and things that you wouldn't plan to use in combat but instead opens up roleplay opportunities. 

They get a pile of abilities through invocations, spells, pact boons, and patron boons, many of which are always available or recharge on a short rest. As mentioned, Eldritch Blast is a great cantrip, and with Agonizing Blast + Hex you can stack damage on each blast, turning you into a potent "archer". Finally, they ooze flavour and give you lots of RP potential.

Hi guys, thanks for your responses. I didn't consider about regaining the spell slots used after short rest, that makes it less painful.

I was more inclined to the chain or the tome pacts, cause I'm not really into fightings, except for bothering others at distance haha. Considering that, I'm gonna examine possible synergies for the eldritch blast. If I have it covered up the battle aspect (to not be just a squishy useless party member when bad times arise) I can think more on the roleplay and the plot possibilties.

I think they are the premiere choice for multiclassing as well.  The great benefits you get very early on, best damaging cantrip in the game, invocations, recharge slots on short rest.  There's a LOT of really good stuff packed into this class and a lot of it you can have for a small investment.  Also since it's a Cha based class that fits well with the largest number of other classes as well.  I use a dip of warlock in a lot of my characters for both the wonderful flavor and the utility it adds.

1. Force damage at will. There's a SCAG cantrip that also does so, but it requires you to wade into melee, which casters should not be doing.

2. If your group is good at getting short rests in, having your 5th level slots recharge on a short rest lets you churn out spells like Dimension Door, Telekinesis, Black Tentacles, Conjure Elemental, Invisibility affecting four people, and so on. Also, during Storm King's Thunder, I used Sending a lot to keep one of the factions notified about everything that was happening even out in the field.

Role play wise there are quite the variety of possibilities from warlocks as a whole.  Just because you take a pact with a fiend does not mean you are automatically evil.  Which I think makes for even MORe interesting options.

a thing to remember is that the warlock is not trying to compete with wizards and sorcs as a spell caster

there competing  against rangers or paladins and hybrid hitters or supporters 

With the right invocations and feats, Eldritch Blast has a range of 600 feet. Thats one reason to choose warlock!

Quote from DukeForau >>

With the right invocations and feats, Eldritch Blast has a range of 600 feet. Thats one reason to choose warlock!

Quote from HeroZero >>

Quote from DukeForau >>

With the right invocations and feats, Eldritch Blast has a range of 600 feet. Thats one reason to choose warlock!

 Not sure where feats come into it but F yeah Eldritch blast can become a beast of an attack.

 oh, oh my.  Can't say I have looked at spell sniper.  Talk about sniping... I see an owlbear two ridge lines over.  Aaaannnnd its dead.  : )

Eldritch blast is huge.    One of my favorite tricks is to go Great Old One, and get the spells like Grasping Tentacles.   Use the pull / push Invocations on Eldritch Blast, and you can keep the monsters inside the tentacles if they try to escape, or if you can't get them all in at once.  

Hex is another fun spell, especially with all the new little Invocations you can use with it.  

Familiars that can turn invisible and fly and you can see through their eyes make them one of the best scouting options in the game.

The warlock is the real arcane archer (leaving pact of the blade aside for now). You don't really feel like a full caster, since your spell slots are so limited, but instead you spam eldritch blast all day, making your role ranged damage dealer. Your spell slots should be used to bolster the aforementioned role, or shore up your weaknesses. What makes playing a warlock really interesting are the few unique warlock spells, your connection and involvement with your patron (choose a cool one), and your invocations! The invocations are very cool, and allow you to do things that really set you apart. See perfectly through magical darkness, give yourself temp hit points at will, give yourself swim speed and water breathing, improve your eldritch blasts, speak with the dead at will, never have to sleep again, see through solid objects and cast invisibility or hold monster at will toward the later levels. And many more.

Currently I'm playing a Half-Elf Pact of the Chain Archfey Warlock from the Feywild, with a focus on nature skills. My patron is Nicnevin the Queen of Witches (Archfey from The Tome of Beasts). About to reach lvl 7, at which point my abilites and spells will look something like:

Class Features

- Frighten or Charm in a 10ft cone in front of me (once per short rest). Eh it's something. Fiend got all the good stuff ;)

- Teleport 60ft away and turn invisible if I take damage (once per short rest).

- Got a Sprite (scout, invisible, adorable, adds a lot to the RP side) / Pseudodragon (gives you Magic Resistance when near you). 

Invocations

- Add +CHA bonus to eldritch blast damage (Agonizing Blast).

- 120ft perfect vision, see through magical darkness (Devil's Sight).

- Always start every combat with 8 extra temp HP (Fiendish Vigor).

- Slow a creature by 10ft for each hit from Eldritch Blast (Lance of Lethargy). Good luck running away with -20ft speed.

Spells 

0 - Eldritch Blast (your bread and butter ranged attack)

0 - Magic Stone (to hand out to familars and other npcs)

1 - Hex (occasionally good to hamper someones checks, and increases your damage by ~33% at 20 CHA. Rarely use it since I have other cool things to use concentration on)

2 - Hold Person (scales with level, at lvl 7 you can hold 3 humanoids)

2 - Mirror Image (good defense for a tight spot, without needing concentration)

2 - Shatter (need some sort of AoE for clusters, or when you need to break some sort of structure)

3 - Counterspell (a little bit weak for warlocks, but sometimes you need to counter some bullshit)

3 - Plant Growth (100ft radius aoe, 1/4 move to slow down your opponents. A melee creature effected by this is dead before he can reach anything)

4 - Greater Invisibility (this pretty much replaces hex. You have advantage on every attack, while attacks on you have disadvantage. Opportunity attack, what's that? Incredible spell for a warlock. You'll pretty much never not be invisible again in combat. Shadow of Moil is similar for non-archfey warlocks)

4 - Dimension Door (500ft teleport with a friend for when shit really hits the fan)

Eldritch Blaster = gunner?   *hmm*  Has potential if you think of it that way.  

And lets not forget the popular Darkness / Devil's Sight combination.

Another fun thing to do is combine Silence (ritual cast) with one of the Invisibility Invocations.  No sound OR sight to be seen. 

Pact Rod, if you get one, makes you really good at disabling spells, since it jacks your DC up fairly high.

Hex, interestingly enough, I tend to use less for combat and more for social situations.  See, Hex someone's Wisdom or Charisma, get an ally or familiar to Help you, and social-fu your way through any conversation with Advantage while the opponent has Disadvantage.  Social situations tend to be restful areas as well, so short rest to recover the spell slot.

Short remark on Lance of Lethargy: the Invocation works only once per turn.

Good call, I'm leaning towards Repelling Blast atm.

 Understandable - Lance of Lethargy hitting the same person four times (or whatever) would effectively paralyze them, and I'm sure that's what they're trying to avoid.   That said, repelling blast is generally better than LoL, even if the latter could stack.  Positioning has tactical considerations above just slower movements. 

That's the thing with the warlock.  There's some very good options there, but also a good number of lackluster options.

I'm actually with Rhymfaxe on the fact that the Warlock is much morel like an Archer then a traditional caster.

I just made a Tiefling Warlock: Celestial, pact of the Tome.  Only played 1 game so far.  The conceit of the character is he is trying to prove that Tieflings aren't all bad, wasn't allowed to be a Paladin, so he made a deal with an Angel.  He sees himself as "A big damn hero", I play him like he's a Paladin.  Pact of the Tome helps me make up for the fact that we don't have a Wizard. 

What I like about the the Warlock is that even above who your Pact is with the type of Pact really defines the character.

With Pact of the Celestial once I hit 6th lvl I'll add my Charisma to all Fire and Radiant damage (Radiant Soul) and I took Flames of Phlegethos so when I cast a fire spell I am surrounded by fire and anyone attacking me takes 1d4 fire damage.  My character has Eldritch Blast as a backup, but only if something is immune to fire.
With Pact of the Tome I took my 3 cantrips as Firebolt, Shillelagh, and Guidance.  So, how my Radiant Soul will apply to both Firebolt and Shillelagh, because I'm also have Green Flame Blade as a Warlock spell.  This makes me almost a Hexblade because my Quarterstaff deals 1d8 damage and hits/damage is Cha Mod from Shillelagh.  Also by specializing in single attacks (Firebolt and Green Flame Blade) lets my Familiar (from Book of Ancient Secrets gives me Find Familiar) gives me Advantage on 1 attack a turn.

At this point I'm expecting my 2 spells / short rest to mostly be used for utility.  With everything I kind of look like a Wizard (familiar and Ritual spells), I kind of look like a Paladin (in melee combat hitting and damage with Charisma), I kinda look like a Warlock (with the spells and Invocations), and I kinda look like a Cleric (Celestial Pact giving Healing Light and Cure Wounds and Restoration to my list)...  I would say I'm not nearly as powerful as anyone focused in any area... but I touch a lot of bases.

The thing that makes the Warlock's Otherworldly Patron ability. Dark one's blessing is so OP, it's almost like god modding. What also makes it good is the Edritch blast