Fighter Subclass: Arcane Arm

Arcane Arm

Your non-dexterous arm becomes arcane, changing in appearance, and granting you the following traits:

• You gain a +1 bonus to AC while wearing no armor
• Your unarmed strikes deal 1d6 + your Strength modifier in slashing damage when using that arm.

Arcane Arm Modes

You learn 2 Arcane Arm Modes of your choice from the list at the end, which you can activate a number of times equal to your proficiency bonus by using a bonus action in your turn.

You learn an additional Arcane Arm Mode of your choice at 10th level, and another one at 18th level.

You can only activate one Arcane Arm Mode at a time, and you can only use each Arcane Arm Mode a number of times equal to your proficiency bonus. You regain all expended uses when you finish a long rest.

While an Arcane Arm Mode is active you need to maintain concentration on it as if it was a spell, or the arm revert to its normal state.

Imbued Strikes

Starting at 7th level, you add your proficiency bonus to your Arcane Arm Mode actions and damage. You can also change between Arcane Arm Modes as a bonus action.

Master Arcanist

At 10th level, you learn 1 Arcane Arm Mode of your choice. You also no longer need to concentrate while using Arcane Arm Modes.

Multi-Arcanist

At 15th level, you can activate 2 Arcane Arm Modes at once, having to select which trait to keep when those overlap.

Divine Arcanist

At 18th level, you learn 1 Arcane Arm Mode of your choice. You can now activate Arcane Arm Modes at will, and use a free action to activate, deactivate and switch between Arcane Arm Modes.

Art by DALL·E

Arcane Arm Modes

Bestial Arm

Your arm grows bestial claws and fur. While this mode is active, you gain the following benefits:

• Armor Bonus. You gain a +1 extra bonus to AC while wearing no armor.
• Multiattack. Whenever you take the attack action, you can make an additional unarmed strike as a free action.
• Bestial Damage. Your unarmed strikes deal 2d8 + your Strength modifier in slashing damage when using that arm.

Elemental Arm

Your arm becomes of the element that you chose when activating this mode (ice, fire or thunder), granting you the following benefits:

• Damage Resistance. You gain resistance to the damage type of your element.
• Elemental Spellcasting. Once every time you activate this mode, you can cast a spell corresponding to your element as a 1st-level spell. The spell is cast using your Strength modifier as your spellcasting ability modifier.
• Elemental Damage. Your unarmed strikes deal 1d6 + your Strength modifier in elemental damage when using that arm.

Element	Spell
Fire	Burning Hands
Ice	Ice Knife
Thunder	Thunderwave

Vampiric Arm

Your arm becomes pale and cold, and you gain the following benefits:

• Damage Resistance. You gain resistance to necrotic damage.
• Vampiric Spellcasting. Once every time you activate this mode, you can cast the spell Vampiric Touch as a 1st-level spell. The spell is cast using your Strength modifier as your spellcasting ability modifier.
• Vampiric Damage. Your unarmed strikes deal 1d8 + your Strength modifier in necrotic damage when using that arm. You regain hit points equal to half the damage dealt by this attack.

Draconic Arm

loaded with dragon resistances and breath weapons

Your arm becomes scaly and draconic, of the ancestry of your choice when activating this mode, and you gain the following benefits:

• Damage Resistance. You gain resistance to the damage type of your draconic ancestry.
• Dragon Breath. Once every time you activate this mode, you can use your action to exhale destructive energy. Your draconic ancestry determines the size, shape, and damage type of the exhalation.
• Dragon Damage. Your unarmed strikes deal 2d6 + your Strength modifier in damage of the type of your draconic ancestry when using that arm.

Draconic Ancestry	Breath Weapon
Black	5 by 30 ft. line (Acid)
Blue	5 by 30 ft. line (Lightning)
Brass	5 by 30 ft. line (Fire)
Bronze	5 by 30 ft. line (Lightning)
Copper	5 by 30 ft. line (Acid)
Gold	15 ft. cone (Fire)
Green	15 ft. cone (Poison)
Red	15 ft. cone (Fire)
Silver	15 ft. cone (Cold)
White	15 ft. cone (Cold)

Rust Arm

Your arm grows a bug-like carapace, and you gain the following benefits:

• Iron Scent. Your arm can pinpoint the location of ferrous metal within 30 feet of it.
• Rust Metal. Any nonmagical weapon made of metal that hits you corrodes. After dealing damage, the weapon takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed. Nonmagical ammunition made of metal that hits you is destroyed after dealing damage.
• Rust Damage. Your unarmed strikes deal 1d8 + your Strength modifier in acid damage when using that arm. After attacking with this arm, if the target is wearing metal armor or a metal shield, it takes a permanent and cumulative −1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10. A shield is destroyed if the penalty reduces its AC to 0.