Hello all, I'm building a new base class for D&D 5e. I'm going to be allowing it into my home games to do some balance testing, but I'd really like to hear if there's any major issues with it before doing so. (To minimize the amount of ret-conning I need to do.) I'm hoping some people would be willing to provide some feedback on the class, both mechanically and thematically.

Essentially, this is a mechanical mix between Barbarian, Sorcerer and Warlock features and thematically it's an elemental force trapped in a mortal body (or a mortal body haunted by an elemental, depending on who you ask). It is a somewhat weak and unassuming kind of character; a very poor spellcaster with no special features, until it explodes into elemental fury. At that point, it's a force to be reckoned with, at least until it runs out of steam. Unlike most full spellcasters, the Spellfury does not get 6th level or higher spells, but it makes up for this with a lot of lower level spells. The toughest choice as a Spellfury will always be "How brightly do I want to burn right now?", as you have pretty strong control over how quickly you spend your limited spell resources.

Looking forward to any feedback and thanks for taking the time to read through this! :)

Amid the laughter, a frail human feels his blood burn and boil with anger. Then it spills forth, literal fire bursting from his body before he explodes in a blast of flames that burn down the Inn in seconds, leaving only a frail, humanoid fire elemental standing.
With three springy steps, the small Halfling bounces towards the Orcish mob. As she touches down on the last, her body becomes tidal wave, sweeping up the Orcs. The wave rolls the Orcs down the battlefield and deposits them in a large heap as a Halfling-sized water elemental reforms from the wave.
An exploding Fireball throws up a cloud of black smoke and burning heat where the Elf stood. As the smoke dies, a grinning humanoid tower of rock appears from the crater, unbothered by the destruction around it.

Spellfuries are the raw form and strength of the elements, contained in a flimsy mortal shell. They are a bizarre union of the creatures of Material Plane and the roiling Elemental Chaos, whether forged by strange rituals, born from the union of elemental beings and mortals, or sprung whole from the Chaos. When Spellfuries are calm, they are like ordinary creatures, but when their emotions heighten, their passion burns, their gaze chills or they explode in fury quite literally.

Barely contained power
Spellfuries rarely live a normal life, the churning elements within them forcing them to a life of extremes. Bullying a Spellfury can be dangerous, and more than one has taken to the road after accidentally burning down their entire village. Likewise, forming passionate bonds with others carries an inherent risk. Tragic stories of Spellfuries passionately destroying what they love are many a Bard's favorite, but also further drive Spellfuries to be careful in their bonds and friendships.

Many adventure with mercenary companies, or even travel the vast roads of the world alone, just so they do not risk experiencing too many emotions they cannot handle around those they care for. As a result, Spellfuries can be distant, even seeming uncaring of long known friends and colleagues, until they are pushed to an edge.

But when the push comes, and the flimsy mortal shell is traded for the raw fury of the elements, Spellfuries unleash their true emotions. Dangerous when provoked by those they hate, but also highly protective of those they love, triggered Spellfuries burn a path through any battlefield as easily as they burn relationships with colleagues they've long disliked but never openly confronted.

Creating a Spellfury
When creating a Spellfury, think about which elements resides inside you most. While you will be able to manifest an array of abilities and spells, your body will mostly take the shape of one of the 4 classical elements. Also think about how your element affects your personality; are you tough and dependable as stone, do you flow through life like water, do you push those close to you away to protect them from your fire, or do you smash into people's lives like a thunderstorm? Does your character embrace their elemental heritage, or hide from it?
How do you resist the elements bursting forth when you do not wish them to? Do you have rituals, sayings, or other ways to keep yourself calm? How does your elemental form manifest? How does your personality change when you let it all out? Do you become overly protective of friends, or the doom of your enemies? Do you wish to cool down tensions, or spark conflict? And how do you look back on your actions when you return to your other form? Do you long for the next change of living to the fullest, or dread the next time you lose control?

Quick Build
You can make a Spellfury quickly by following these suggestions.
First, Charisma should be your highest ability score, followed by Constitution.
Second, choose the hermit or outlander background.
Third, choose the dancing lights, chill touch, firebolt and acid splash cantrips, along with the 1st-level spells thunderwave and witch bolt.

Spellfury - Core features

Level:	Prof Bonus:	Features:			Furies/day:	Fury points:
1	+2		Fury, Furious spells		2		2
2	+2		Elemental Manifestation		2		3
3	+2		Elemental Body			3		4
4	+2		ASI				3		4
5	+3		-				3		7
6	+3		Elemental Manifestation		4		7
7	+3		-				4		8
8	+3		ASI				4		9
9	+4		-				4		10
10	+4		Elemental Manifestation		4		11
11	+4		Breach the Fury			4		12
12	+4		ASI				5		12
13	+5		Elemental Body			5		12
14	+5		Elemental Manifestation		5		13
15	+5		Devour Elements			5		13
16	+5		ASI				5		13
17	+6		Tempest Body			6		14
18	+6		Elemental Manifestation		6		14
19	+6		ASI				6		14
20	+6		Purity of the Elements		6		15
Spellfury - Basic Spellcasting

Level	Cantrips known	Spells known	Max spell level		1st	2nd	3rd	4th	5th
1	4		2		1			-	-	-	-	-
2	4		3		1			1	-	-	-	-
3	4		4		2			1	-	-	-	-
4	5		5		2			1	1	-	-	-
5	5		6		3			2	1	-	-	-
6	5		7		3			2	1	-	-	-
7	5		8		4			3	1	-	-	-
8	5		9		4			4	1	-	-	-
9	5		10		5			4	2	1	-	-
10	6		11		5			4	3	1	-	-
11	6		12		5			4	3	1	-	-
12	6		12		5			4	3	1	-	-
13	6		13		5			4	3	1	1	-
14	6		13		5			4	3	2	1	-
15	6		14		5			4	3	2	1	-
16	6		14		5			4	3	2	1	-
17	6		15		5			4	3	3	1	1
18	6		15		5			4	3	3	2	1
19	6		15		5			4	3	3	2	1
20	6		15		5			4	3	3	2	1
As a Spellfury you gain the following features:

Hit Dice: 1d6 per Spellfury Level
Hit Points at 1st Level: 6 + your Constitution Modifier
Hit Points at Higher Levels: 1d6 (or 4) + your Constitution Modifier per Spellfury Level after 1st

Armor: None
Weapons: Daggers, darts, slings, quarterstaffs, light crossbows
Tools: None
Saving Throws: Constitution, Charisma
Skills: Choose two from Arcana, Deception, Insight, Intimidation, Persuasion, and Religion

You start with the following equipment, in addition to the equipment granted by your background:

  • (a) a light crossbow and 20 bolts or (b) any simple
  • (a) a component pouch or (b) an arcane focus
  • (a) a dungeoneer's pack or (b) an explorer's pack
  • Two daggers

You learn and cast spells exactly the way a Sorcerer does, also using Charisma as your stat. (Abbreviated to save people from reading things they already know.)

A few times per day, you can unleash your inner power and enter a Fury by spending a Bonus Action on your turn. While in a Fury, you gain a number of Fury points (see table), which you can spend to power your some of your abilities, or use to cast additional spells. When your Fury ends, any unspent points vanish.

Your Fury lasts for 1 minute. It ends early if you do not cast a spell or use a manifestation that can deal elemental damage on your turn, or if you spend a Bonus Action to end it on your turn. (Elemental damages are Fire, Cold, Lightning, Thunder and Acid)

Once you have entered Fury a number of times shown for your Spellfury level in the table, you must finish a long rest before you can enter Fury again.

You can convert Fury into spells. When you cast a spell, you may spend an amount of Fury as shown in the table to cast it at the given level, without spending one of your normal spell slots. You cannot create a slot higher than your "Max spell level" as shown on the "Spellfury - Basic Spellcasting" table.

Creating spellslots
Spellslot level:	Fury cost:
1st			2
2nd			3
3rd			5
4th			6
5th			7
Starting at 2nd level, the elemental energies whirling within you can manifest while you are in Fury.
Pick one of the elemental manifestations listed below that you qualify for.
You can pick additional Manifestations at levels 6, 10, 14 and 18.

- Burning blood [requires level 2]
While in Fury, when you are hit by a Melee Attack, flaming blood can spray from the wound.
You can use your Reaction to spend any number of Fury Points, dealing the creature that struck you 1d6 Fire damage per point of Fury spent.

- Earthen skin [requires level 2]
While in Fury, when you take damage from a weapon attack, your body can take on the hardness of stone.
You can use your Reaction to spend any number of Fury Points, reducing the damage taken by 1d6 per point of Fury spent.

- Flowing form [requires level 2]
While in Fury, when you take damage, your body can flow like water, removing you from danger.
After taking the damage, you can use your Reaction to spend any number of Fury Points, moving 10 feet per point spent.

- Empowered form [requires level 6]
While in Fury, you can enhance the strength of your elemental magic.
As a Bonus Action on your turn, you can spend 2 Fury Points and choose Fire, Acid, Lightning, Cold, or Thunder.
While the Fury lasts, whenever you cast a spell of 1st or higher that deals damage of that type, increase the damage dealt by your Charisma modifier.

- Exploding flame [requires level 6]
While in Fury, you can explode into flame.
As an Action on your turn, spend any number of Fury Points. Creatures within 10 feet of you must make a Dexterity Saving Throw or take 1d8 Fire damage per point of Fury spent.

- Vortex [requires level 6]
While in Fury, you can turn into a cloud that rapidly moves to a new position.
As a Bonus Action on your turn, you can spend 2 Fury Points to teleport up to half your speed.

- Matching form [requires level 10]
While in Fury, you can change your form to match that of an attacker.
As a Bonus Action on your turn, you can spend 3 Fury Points to gain Resistance to Fire, Acid, Lightning, Cold, or Thunder while your Fury lasts.
If you use this Manifestation again during the same Fury, the previous effect is lost.

- Thundering form [requires level 10]
While in Fury, you can change into a thunderstorm that plows over the battlefield.
As an Action on your turn, you can spend 3 Fury Points to move up to your speed. For this movement, you do not Provoke opportunity attacks and can move through hostile creatures.
Any creature whose space you entered during this move must make a Strength Saving Throw against your Spell DC or be knocked Prone.

- Barrier [requires level 10]
While in Fury, you can grow a body of solid rock.
As a Bonus Action on your turn, spend any number of Fury Points and gain 1d10 temporary hit points for each.

- Overpowering burst [requires level 14]
While in Fury, when you cast a spell, you can give extra power.
When you cast a spell of 1st level or higher, you can spend extra Fury Points equal to the spell's level to make one target of that spell roll its first saving throw with Disadvantage.
You can use apply this Manifestation more than once, by paying the cost for each target.

- Ignite [requires level 14]
While in Fury, your fire spells cling to targets, burning them further.
When you deal Fire damage to a target, you can spend up to 8 Fury Points to have that creature take 1d6 points of Fire damage per point spent at the start of each their turns.
This effect lasts until the creature takes an Action and succeeds on a Dexterity Check against your Spell Save DC to douse itself, or until your Fury ends.

- Roiling wave [requires level 14]
While in Fury, you can turn into a rushing wave that sweeps away those it hits.
As an Action, spend 6 Fury Points. You become Large until the end of your turn and you can enter a hostile creature's space and stop there.
Any hostile creature of size Large or smaller whose space you enter must make a Strength Saving Throw against your Spell DC or be swept up by you and take 2d6 cold damage.
Any friendly creature of size Large or smaller whose space you enter may chose to be swept up by you, taking no damage.
When you move, any creature you have swept up is moved along with you, remaining inside your area.
At the end of your turn, if any creatures are sharing your space, they are ejected out of your occupied area before you return to Medium size.

- Unstoppable force [requires level 18]
While in Fury, your energies are so powerful, they become nearly unstoppable.
When you can cast a spell that deals elemental damage, you can spend Fury Points equal to the spell's level to let that spell overcome Resistance and Immunity.
The spell bypasses Resistance entirely, and deals half damage to any creature normally Immune to the damage.

- Perfect form [requires level 18]
While in Fury, you can change your form to perfectly match that of an attacker.
As a Bonus Action on your turn, you can spend 7 Fury Points to gain Immunity to Fire, Acid, Lightning, Cold, or Thunder while your Fury lasts.
If you use this Manifestation again during the same Fury, the previous effect is lost.

Starting at 3rd level, your Fury permanently manifests in elemental forms when unleashed.
Pick one of the Elemental Bodies listed below. While your Fury is active, you gain the benefits of the chosen body.
You can pick a second Elemental Body at 13th level. You select which Body to use whenever you start a Fury.

- Body of Fire
Your body erupts into flame. You have Resistance to Fire Damage.
Any creature that starts its turn within 5 feet of you, takes 1d8 Fire Damage.
This damage increases to 2d8 at 11th level, and 3d8 at 17th level.

- Body of Earth
Your body becomes heavy, solid rock. You have Advantage on Saving Throws to resist being knocked prone or moved against your will.
When you are attacked, you can use your Reaction to gain Resistance to all damage for that Attack.

Body of Water
Your body becomes a sloshing shape of water. You can move through enemies, but you cannot stop in their area.
Enemies making an Opportunity Attack against you have Disadvantage on the roll.

Body of Air
Your body becomes a whirling vortex of thunder and lightning. You have Resistance to Lightning and Thunder.
Whenever one of your 1st level or higher spells deals deals Lightning or Thunder damage, any target hit must make a Strength Saving Throw against your Spell DC or be knocked prone.

At 11th level, the energies inside you are so potent they can burst free when they sense you are in danger.
If you take damage that reduces you to 0 hit points but does not kill you outright, if you have any Furies left, you can spend any number of Hit Dice as a free action.
Your HP total becomes the total number of HP rolled and you immediately start a (new) Fury.
If you were already in a Fury, your Fury Points are reset to the normal limit for a Fury. You can pick a new Body for this Fury, if desired.
Once you have used this feature, you cannot use it again until you have taken a Long Rest.

At 15th level, you can drain elemental energy from your surroundings and use it to strengthen yourself.
While in a Fury, whenever you take elemental damage, you gain 2 Fury points.

At 17th level, the energies within you begin to mix. When you start a Fury, you may choose to gain the bonuses of both your Elemental Bodies.

At 20th level, when your Fury is unleashed, you can take on the form of a pure element while it lasts.
You may use this option when you start a Fury. You take on the form of a Water, Fire, Air or Earth elemental.
Use the statistics of the selected Elemental, except you retain your mental statistics and you can still use your Fury abilities (including spellcasting).
If your Elemental form is reduced to 0hp, your Fury ends and you revert to your normal form.
Once you use this option, you cannot use it again until you finish a Short Rest or Long Rest.