Hello there, I’m currently trying to build a character for our upcoming Descent into Avernus campaign. I have a general idea of what i want to play, but i’m having a hard time committing to a build. There are so many variants and options spinning in my head, so i’d really appreciate a couple of fresh eyes to have a look and add some new input or giving a viabilty check to my ideas.

So, in general... i think i suffer from a serious case of „i want it all!“, so i fear that my build will be all over the place and not really good at anything. I really enjoy optimizing, but only in a set framework. In the end the build should reflect the theme of the character i had in mind. But i’m getting ahead of myself...

We rolled for stats and i got a 17, 15, 14, 12, 11, 7

So, i  kind of want a greatsword wielding, lightning charged fighter. I really enjoy high mobility and some kind of low tier battlefield control. Concerning race, i’m leaning towards an Aasimar, mainly because i hope for some juicy drama when we descent to hell, and also because i really like the image of some dude with incorporeal wings of stormy clouds with lightning in them...

So my first idea was an Eldritch Knight/Genie Warlock multiclass, maybe something like EK8/WL4-5 The EK brings all the nice 1st lvl defensive spells and with war magic i can incorporate some juicy booming blades or maybe some mortal combat style „get over here“ lightning lure pulls followed by a weapon attack. Of course I’d get warcaster for more BBs on opportunity attacks.

The Genie warlock gives a small thunder dmg boost on one attack, a nice place to chill and hoard stuff, some more spell options, misty step for example, mirror image, or even thunderstep and spirit shroud when i make it to WL5. Pact of the tome could add some more utility outside of combat. Chainlock might also be nice, i love the idea of a reflavored familiar in a cute air elemental like appearance... But apart from coming online rather late with the whole warmagic on level 7 thing, i wonder if my damage would be too inconsistent or lackluster. I guess i could get GWM, but i kinda don’t feel this feat. When i take the expected 65% hit chance baseline, then the -5/+10 wouldn’t even really do more damage overall. Although i have to admit that i completely lack real experience in that regard.

So then the allmighty battlemaster clawed itself into my head. The Brace maneuver could add more chances to apply Booming Blade, albeit i guess without the bonus damage but with the Genies Wrath and Aasimar bonus dmg at least. Pushing attack on the other hand could force some BB bonus dmg, when the enemy needs to get close again.

I could get to fighter 3 for the Subclass and then switch to Warlock and get Pact of the Blade. Of course multi attack on level 8 is very dissapointing, but the added bonus dmg from genies wrath, booming blade and maybe a maneuver could maybe mitigate it a bit? With this build i can have a bit more control options via maneuvers, and i could emphasize the feel of a blademaster. But i would have a lot less spell slots over the day, and i’d lose my beloved 1st level defensive spells. I guess i could squeeze in 1 or 2 levels of sorcerer? But man... a 3 class multiclass seems a bit... messy. Also my total HP would really take a hit with all those caster levels

I should maybe give an honorary mention to the popular EK and Warmagic Wizard multiclass. I guess that could also work, but i kinda like the whole genie flavor.

But apart from that... i feel a bit stuck. I’d really love some input or even experience from you guys. Maybe there is a perfect combo or class alternative i haven’t really thought of. But i have to say in advance, i definitely don’t want to go paladin or Barbarian. I really don’t like those classes ;D

Oh, and a few words to the rest of the group: We’ll be 5 players and a dm. Two of those players i know really well, and they are more of the „meeh, some basic optimization is nice, but i don’t need it that much“ type, and the other two are new. But they have a lot of experience and will probably not build something weak. I don’t know how much combat we’ll have, but we all enjoy a nice mix of RP heavy sessions and some good ol‘ murderin‘ the forces of evil.

So thanks if you stuck with me until now, cheers!

Check out tempest cleric. Just straight through. You’ll still get the martial proficiency to use that greatsword. You’ll get some good AoE spells and lots of lightning powers. 

It’s too bad you are anti-Barbarian because this character idea screams Storm Herald Barbarian to me.  You get the martial weapons and the lightning aura.

Another possibility would be the battlemaster and a storm sorceror MC. 

As with others it feels like Fighter is the wrong class for this idea; an Artificer Battle Smith might work better, or even Paladin and just ask your DM if you can swap radiant damage for lightning. Fighter seems like the wrong framework to use, as you'd need to multiclass to get the things you want but that comes with significant drawbacks.

You could consider Wizard - Bladesinger and reflavour spells. I did that with a lightning character and it was fantastic. I went with rapier, so I didn't have to be MAD.

With Tasha's to decide stats you could have 18 Dex, 16 Int. With Mage Armour that is AC 20 at 2nd level, with option to use Shield for a round of AC 25. These can be flavoured as lightning-enhanced speed or electromagnetic repulsion.

I'd recommend Tiefling if DM allows and reflavour Hellish Rebuke to lightning damage. 

You'd start with a dagger and making use of Green-Flame Blade reflavoured as lightning, or perhaps lightning lure / shocking grasp.

At level 2, you really start to shine, able to stab and evade like a pro. Absorb Elements would also be spiffy. And you have spells to enhance this - be it the speed of expeditious retreat, haste, and the offensive like lightning bolt. As mentioned, consider reflavouring spells like Scorching Ray into Zapping Bolts. At level 6, earlier than the EK build, you can attack and do a cantrip in the same action without using up a bonus AND if you're hasted you can do two attacks and a cantrip with a bonus action. 

Worth considering, maybe?

While bladesinger makes a certain amount of sense I noticed that there are no lightning specific spells after L6 Chain Lightning so it might be better to aim for something like bladesinger 6/ storm sorceror 14 to get the extra attacks and to get the transmuted spell metamagic that would let you convert just about any damage dealing spell spell to a lightning spell upto 14 times a day. That would mean AC 12(studded leather) + DB(+5?) or mage armor + DB, either 2 attacks or an attack and a cantrip, full spellslot progression, 7th level spells and 14 converted to lightning spells a day.
if you want somewhat different possibilities there are a couple of bard combat styles as well as artificer or even 5 levels in a ranger or warlock subclass with the loss of some spell slots at the high end. Each offers perhaps a little more than a fighter MC for this as they all give some sort of spell progression in addition to the combat proficiencies. Fighter gives you none effectively.

Descent into Avernus ends around level 13-14. So Warlock 5 means you would lose out on third attack and 3rd-level EK spells. You would also have two casting stats, and both of them will be on the low side if you have to meet multiclassing thresholds. That makes your Lightning Lure move and other battlefield control spells not so great since they would have a low DC.

Are the pact magic spell slots and pact boon worth it? Five levels of EK spell progression also gives you additional slots, so the pact magic only pulls ahead at 2+ short rests per day. As for the boon, Blade overlaps with EK bonded weapon, Chain is a souped up Find Familiar, and you can pick up most of Tome with a Ritual Caster feat. So you have options to get similar effects without multiclassing.

Personally, I’d just go straight EK and reflavor the spells and abilities to fit the theme. Thunder booms when you summon your bonded weapon to your hand. A lattice of electricity surrounds you as a Shield, making you harder to hit. Lightning arcs to your destination when you Misty Step (you can take this as one of your limited non-abjuration/evocation spells). The only thing you’d be missing is the genie bottle, but if you really really want that then you only need Warlock 1 for it.

As you’ve seen from the posts there are a lot of possibilities for a melee PC with lightning spells. A major question is which you want dominant- the melee or the spells. If melee then the initial builds are fairly reasonable. You might consider storm sorceror for more cantrips, spells and slots and the transmute spell metamagic instead of the gene warlock. Bladesinger won’t work if you want to wield a greatsword. In addition to the battlemaster and EK you might want to look at the samurai (the to-dachi is a great sword). Personally I prefer sorcerors to warlocks  and the transmute spell metamagic let’s you turn pretty much any damage spell into a lightning based one but it does make the build MAD  but then so does basically any casting class MC. If mobility and battlefield control are interests then you might want to look at the ranger rather than the fighter. The subclasses all give a way to get a third attack at L11, the spell progression is better than for the EK but you don’t get heavy armor but half plate +2DB works nearly as well. 

Hi, thanks for all the nice input. I definitely should have specified more that the character should be a fighter first with his stormy magic being more of a supplement for his fighting style.

A little birdy told me that pretty much all of avernus will be resistant to lightning damage and often magic in general and magic users won't have a particular fun time, except when they go for buffing. So I'm not even trying to use magic in an offensive manner. So the MADness of the casting modifier wouldn't really matter that much. And with damage spells out of the picture, there isn't much going on with the available spell list, as the really nice defensive spells of 2nd level are all illusion, weirdly... Hence the whole multiclass idea.
One of the reasons why I thought about the Genie Warlock was the bonus thunder dmg, which almost nobody is resistant to. Of course it's only PB dmg and only once per turn, but it instantly gives a nice stormy flair and it scales with character level. And the battlemaster gets some maneuvers to apply that damage on his reactions. Warcaster would enable Booming Blade, so those reaction attacks could really be some decent hits. The level 6 feature is also nice, more ways to fly without concentration...

Right now i'm leaning more towards a battlemaster build, since that offers more variety at lower levels. And let's say i really want those 1st level genie benefits, would you recommend leaving it at a 1 level dip, and get some sorcerer levels later for the defensive spells and a quickened booming blade once in a while? With Aasimar as a race the divine soul would fit thematically. Storm sorcery is just so bad unfortunately.

Concerning the Bladesinger, it crossed my mind at some point. The subclass looks incredibly powerful especially with their better version of wac magic, but it's meant for elves and half-elves. Yes, there is a clause, but for me that feels like cheating. Also i'm pretty adamant on the whole greatsword...

Quote from Wi1dBi11 >>

If mobility and battlefield control are interests then you might want to look at the ranger rather than the fighter.

 Since you recommended my favorite class: how would you build a stormy thunder ranger?

Protector Aasimar ranger 1 then Sorceror 1. S17/D14/C15/I7/W12/Ch11 which gives you S17/D14/C15/I7/W13/Ch13 with the ASIs at bonuses. While I generally recommend taking the martial class to L5 first I’ve found that taking the sorceror level as L2  is worth the delay as you get the cantrips and spells and then going R2/S1 gets you ramped up on the multiclass spell slot chart. From there I would stay ranger to R6/S1. With that I would take the defensive fighting style and horizon walker. At R4 instead of ASIs I would take the fighting initiate feat to get GWF. R5 gives the second attack and R6 gives you an third L2 spell slot. Then go R6/S2 then back to ranger to R11/S2. At R8 I would improve strength and constitution then get to HW9 for haste and HW11 for the  the additional attack. After that I would add sorceror 3 if you can to get L2 spells and metamagic and sorcery point. Here is my version of the basic character without magic items and only S1-spells and starting equipment. 

https://www.dndbeyond.com/sheet-pdfs/wcwilson82355_69198225.pdf

Battlemaster is probably the best fighter subclass for your build. I just did the ranger because you requested it.

Another good Fighter archetype for your idea would be Rune Knight.  You could get Cloud and Storm runes that buff you, which are sort of Storm magic-like.  Plus, you can ise Giant’s Might to make you and your great sword truly large.  Combine that with a multiclass to a Genie Warlock (Djinn) for 2-3 levels and you could be pretty fearsome without using damage spells.

 I think it would be appropriate to be an air genasi or goliath if you went Rune Knight/Genie, but with Tasha’s you could even be any race that’s not small.