Spellblades take to the battlefield with magically enhanced weapons, channeling magic through their weapons and empowering their attacks with elemental energy. Despite the name, neither spells nor blades are required; a spellblade uses raw magical power instead of the structure of spells to grant these effects, and can deliver them through any weapon.

These magical abilities are known as Blade Arts, though a blade is not required to use them - swords, axes, hammers, arrows, and even fists are capable of channeling this magic just as effectively.

Big thank you to MobiusFlip on the Discord of Many Things for their assistance with the elemental effects and looking over this concept in general.

Changelog:

This is the second playtest version of the Spellblade, with a limited number of Blade Arts known instead of having all of them from the start. Some people thought that having attacks of every element made the Fighter too versatile, and this way learning new Blade Arts helps fill out some of the weaker levels.

If on-demand Force/Thunder/Psychic/etc damage remains too powerful, I wouldn't be unwilling to lock the more esoteric ones until 7th level. This would be in line with the classic RPG fighter having basic elements like fire/ice/lightning early and esoteric elements later on, but I feel that customization is just more fun in general.

Spellguard was also changed to a bonus action which gave resistance for 1 minute. Most enemies resist their own damage, so this way you only sacrifice one attack + bonus action for your variable resistance instead of having to use a resisted attack every turn.

Toxic Blade changed to subtract 1d4 from the target's next save (a la Mind Sliver) instead of disadvantage.

Withering Blade changed to prevent healing (a la Chill Touch) instead of lowering maximum HP.

Bonus Proficiencies

Starting at 3rd level, you gain proficiency in Arcana. If you already have proficiency in Arcana, you may instead gain proficiency in one skill of your choice. In addition, if you know any spells, you may use a simple or marital marital weapon as a spellcasting focus.

Arcana

You gain proficiency in Arcana. In addition, if you know any spells, you may use a simple or marital marital weapon as a spellcasting focus.

Choose a Bonus Proficiency

If you already have proficiency in Arcana, you may instead gain proficiency in one skill of your choice. In addition, if you know any spells, you may use a simple or marital marital weapon as a spellcasting focus.

Blade Arts

You learn your choice of three of the following elemental Blade Arts, magical effects which can be used when you take the Attack action during your turn. You learn two additional Blade Arts of your choice at 7th, 10th, and 15th level. You may only use one Blade Art per turn.

The Blade Arts and their effects are detailed below.

• Blazing Blade. Your weapon bursts into flame. On a hit, it deals fire damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to set the target ablaze. It takes 1d4 fire damage at the end of each of its turns until a creature takes an action to extinguish the flames.

• Caustic Blade. Your weapon drips with a corrosive acid. On a hit, it deals acid damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can deal 2d4 acid damage to a different creature of your choice within 5 feet of the target.

• Chilling Blade. Your weapon coats itself with magical frost. On a hit, it deals cold damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can reduce its movement speed by 10 feet until the start of your next turn.

• Mocking Blade. Your weapon shifts in distracting ways, becoming disorienting to look at. On a hit, it deals psychic damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to disorient it. It has disadvantage on the next attack roll it makes before the start of your next turn.

• Mystic Blade. Your weapon is coated with a shimmering field of pure force. On a hit, it deals force damage instead of its normal damage type. Once on your turn when you hit a creature with this weapon, you can choose to ignore the effects of any protective spells such as mage armor, shield, or stoneskin.

• Resounding Blade. Your weapon clashes and clangs against nothing as you swing it, and strikes with the sounding of a gong. On a hit, it deals thunder damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can push it up to 10 feet into an unoccupied space of your choice.

• Shining Blade. Your weapon glows with a bright light. On a hit, it deals radiant damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can use the light to guide an ally's strike. The next attack made against it by a creature other than you before the start of your next turn has advantage.

• Shocking Blade. Your weapon crackles with electricity. On a hit, it deals lightning damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to shock it, preventing it from taking reactions until the start of your next turn.

• Toxic Blade. Your weapon smokes with the fumes of a magical poison. On a hit, it deals poison damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to debilitate it. The targeted creature subtracts 1d4 from the next saving throw it makes before the start of your next turn.

• Withering Blade. Your weapon seems to weather and warp, appearing ancient and cruel. On a hit, it deals necrotic damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to flood it with necrotic energy, and it can't regain Hit Points until the start of your next turn.

Blazing Blade

Your weapon bursts into flame. On a hit, it deals fire damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to set the target ablaze. It takes 1d4 fire damage at the end of each of its turns until a creature takes an action to extinguish the flames.

Caustic Blade

Your weapon drips with a corrosive acid. On a hit, it deals acid damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can deal 2d4 acid damage to a different creature of your choice within 5 feet of the target.

Chilling Blade

Your weapon coats itself with magical frost. On a hit, it deals cold damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can reduce its movement speed by 10 feet until the start of your next turn.

Mocking Blade

Your weapon shifts in distracting ways, becoming disorienting to look at. On a hit, it deals psychic damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to disorient it. It has disadvantage on the next attack roll it makes before the start of your next turn.

Mystic Blade

Your weapon is coated with a shimmering field of pure force. On a hit, it deals force damage instead of its normal damage type. Once on your turn when you hit a creature with this weapon, you can choose to ignore the effects of any protective spells such as mage armor, shield, or stoneskin.

Resounding Blade

Your weapon clashes and clangs against nothing as you swing it, and strikes with the sounding of a gong. On a hit, it deals thunder damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can push it up to 10 feet into an unoccupied space of your choice.

Shining Blade

Your weapon glows with a bright light. On a hit, it deals radiant damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can use the light to guide an ally's strike. The next attack made against it by a creature other than you before the start of your next turn has advantage.

Shocking Blade

Your weapon crackles with electricity. On a hit, it deals lightning damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to shock it, preventing it from taking reactions until the start of your next turn.

Toxic Blade

Your weapon smokes with the fumes of a magical poison. On a hit, it deals poison damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you can choose to debilitate it. The targeted creature subtracts 1d4 from the next saving throw it makes before the start of your next turn.

Withering Blade

Your weapon seems to weather and warp, appearing ancient and cruel. On a hit, it deals necrotic damage instead of its normal damage type. Once on this turn when you hit a creature with this weapon, you choose to flood it with necrotic energy, and it can't regain Hit Points until the start of your next turn.

Blade Beam

As an action, you can fire a Blade Art's elemental energy from your weapon as a ranged attack with 30/60 range. On a hit, the target suffers the usual effects of the attack. Whether or not it hits, the elemental energy then explodes. The target and all creatures within 5 feet of it must then make a Dexterity save (DC = 8 + your proficiency bonus + the higher of your Dexterity and Strength modifiers) or take 2d8 damage of your Blade Art's type. You can use this feature a number of times equal to your proficiency bonus, and you regain spent uses when you finish a short rest.

Spellguard

Starting at 10th level, when you use a Blade Art, you may gain resistance to its damage type for one minute as a bonus action. This resistance remains active even if you use Spellguard to gain resistance to a different damage type. You may use this feature a number of times per long rest equal to your proficiency bonus.

Elemental Empowerment

Starting at 15th level, once per turn, you can deal additional damage equal to your proficiency bonus of the same damage type as your Blade Art when you hit with an attack (no action required).

Spellblade Mastery

Starting at 18th level, when you take the Attack action, you may activate two different Blade Arts at the same time, allowing you to use the additional effects of both. You can also gain resistance to both damage types with Spellguard. You must choose one damage type for your Elemental Empowerment's bonus damage as well as the damage for the attack itself, but they need not be the same type.