Looking for advice on finding the best fit for an elemental subclass

[Matrota]

I started brainstorming about making an old character idea of mine into a homebrew subclass for D&D 5e but I don't know which base class to use for the subclass idea to begin with. Was looking for some advice on the matter.

The base character was a man who underwent a ritual that bound a fire elemental's soul to his own, and as he got stronger he was able to manifest more elemental power. At first he could light his weapon on fire, later his arms which increased his strength, and at some point he could even split the elemental from himself for a time so it could fight alongside him. The pinnacle of his strength happened when he and the elemental would undergo a short period of DBZ-style fusion, where he would become more like an efreeti than a man, letting him fly and such. I feel like it'd make sense for such a thing to be for a caster class, but I'm conflicted cause the original character I'm basing this off of was a swordsman. I was gonna make it a fighter subclass but I feel like it's a little too magical for the typically mundane fighter. Perhaps a warlock where the patron in this case is actually the elemental you bind yourself to, and it grows stronger with you? What are y'all's thoughts?

[Garfunion]

This sound more like RPing. A Sorcerer(dragon) or Warlock(fiend) can be role-played as an infused elemental bound. With spells like Green-flame Blade and Investiture of Flame can pull off what you want.

You could also go down the Storm Herald Barbarian(Desert) and maybe pick up magic initiate for some fire cantrips.

[Old Harry MTX]

Maybe the Eldritch Knight could be the right starting point?

[SpoonR]

Basic question. Is this a fighter who enhances thenself & their attacks with magic? Or a magic-user who can use a sword or who channels magic through the sword?

Right now it sounds more like the first. Is there a limited set of spells that could represent the magicy bits?

[Edea]

*Ability that adds elemental damage to your melee attacks
*Ability to surround self with an elemental aura, increasing defensive attributes and auto-damaging nearby creatures
*Ability to summon an elemental buddy
*Turn into an elemental of sorts, with new movement modes/combat attributes/etc.

Sure looks like a subclass to me.

Eldritch Knight is a Fighter subclass that's literally "add wizzie magic". Bladesinger's a Wizard subclass that's literally "add sword skillz". I would not be overly concerned about the archetype leaning one way or the other with respect to how 'mundane' or 'magical' it is.

I will say, however, that the given sub-set of abilities we're looking at seem to support physical combat, not casting. Assigning it to a base class that's already physically-focused will make it easier to synergize with core class features.

EDIT: Here's just one really rough/skeletal example, an 'elemental tempest' barbarian. I think the idea of adding it to fighter was a good one, I'd go back to that TBH.
3rd Level - elemental protection and auto-damaging elemental aura while raging
6th Level - add elemental damage to reckless attacks
10th Level - summon your elemental buddy, some sort of cooldown time or resource use required (1/short rest? uses a rage?)
14th Level - Turn a rage into an elemental rage, essentially turn into combat super-beast, needs a significant cooldown/resource cost

[GalacticAxekick]

Classes are defined by the source of their power. Two wizards can have totally different abilities, for example, but no matter what, both gain their power by studying magic. A wizard and a sorcerer can have nearly identical abilities, but no matter what, the former gained her power by studying magic, and the latter was born magical.

There are only three classes that draw their power from another creature. The Cleric borrows magic from the god it serves. The Druid borrows magic from the forces of nature (which includes elementals!). And the Warlock forms a pact with a magical creature in exchange for permanent magical power.

"A man who underwent a ritual that bound a fire elemental's soul to his own" sounds nothing like a Cleric.

I could see this as a Druid (with a homebrew version of Wild Shape that grants you elemental shapes!). Druids even gain access to certain swords and armour! The only issue is that Druids don't have personal relationships with the sources of their power, and can flip-flop between various nature-themed abilities. Your character is stuck with one elemental and the fire powers it offers.

I could also see this as a Warlock. Warlocks gain access to swords and armour, and Warlocks are supposed to have personal relationships with the creatures who lend them power (represented in part by their dependence on Charisma and narrow, immutable spell lists). The only downside is the lack of an efreeti form, although the Investiture of Flame spell or a set of features similar to the Phoenix Sorcerer's could serve this role

[Onos]

One of my players is currently running a fairly similar concept, really enjoying a Druid (Circle of Wildfire)/Monk (slightly homebrewed fire-only Way of the Elements). You could speak to your GM about swapping something out to get the Moon Druid Fire Elemental Wild Shape to portray the fusion aspect? Maybe a feat?

[Fnissalot]

Your backstory sounds like a sorcerer to me, and while an eldritch knight would work rather well, WotC published a Pyromancer sorcerer origin in the "not official" plane-shift kaladesh pamphlet (https://media.wizards.com/2017/downloads/magic/Plane-Shift_Kaladesh.pdf). I would multiclass a variant human with magic initiate for green-flame blade beginning as a fighter for 1-4 levels (Echo knights clone could easily be described as your fire elemental) and then pick sorcerer(pyromancer or draconic) or warlock (celestial or fiend).

[Old Harry MTX]

Classes are defined by the source of their power. Two wizards can have totally different abilities, for example, but no matter what, both gain their power by studying magic. A wizard and a sorcerer can have nearly identical abilities, but no matter what, the former gained her power by studying magic, and the latter was born magical.

There are only three classes that draw their power from another creature. The Cleric borrows magic from the god it serves. The Druid borrows magic from the forces of nature (which includes elementals!). And the Warlock forms a pact with a magical creature in exchange for permanent magical power.

"A man who underwent a ritual that bound a fire elemental's soul to his own" sounds nothing like a Cleric.

I could see this as a Druid (with a homebrew version of Wild Shape that grants you elemental shapes!). Druids even gain access to certain swords and armour! The only issue is that Druids don't have personal relationships with the sources of their power, and can flip-flop between various nature-themed abilities. Your character is stuck with one elemental and the fire powers it offers.

I could also see this as a Warlock. Warlocks gain access to swords and armour, and Warlocks are supposed to have personal relationships with the creatures who lend them power (represented in part by their dependence on Charisma and narrow, immutable spell lists). The only downside is the lack of an efreeti form, although the Investiture of Flame spell or a set of features similar to the Phoenix Sorcerer's could serve this role

This is a nice example of a very comprehensive and useful summary, but I wouldn't rule out other solutions a priori. In my opinion any non-caster class could be suitable for a sub-class that suits you, such as a fighter, or even a rogue who uses sneak attacks to fuel some elemental power.

[sandmote]

A wizard and a sorcerer can have nearly identical abilities, but no matter what, the former gained her power by studying magic, and the latter was born magical.

There are only three classes that draw their power from another creature.

Sorcerer can also get their power from other methods:


Sorcerers carry a magical birthright conferred upon them by an exotic bloodline, some otherworldly influence, or exposure to unknown cosmic forces. One can’t study sorcery as one learns a language, any more than one can learn to live a legendary life. (Emphasis mine)

The UA Phoenix Sorcery subclass might be a good place to start, if this is intended to be a heavy spellcaster.