Spellblade

Spellblades are fearsome, specialized fighters who, be it through extensive research and rigorous study, or innate skill, have gained the unique ability to temporarily imbue their weapons with raw arcane power and refined elemental might. These fighters train themselves to seamlessly shift and control the battlefield; planning, preparing and switching through their elemental infusions in order to tackle any opponent and exploit any potential weakness.  

Spellbound

Starting at 3rd level when you take this archetype, you can spend an hour to attune to a non-magical weapon you are proficient with, at which point it is considered magical while in your hands. As such, it can ignore resistances and immunities to non-magical damage.
Starting at 7th level, while you hold the weapon, it also gains a +1 modifier bonus to attack and damage rolls made with it. This bonus increases to +2 at 10th level and +3 at 15th level.
At 18th level, this bonus can also be applied to any weapon you attune to, even if it is already enchanted. The bonus is applied on top of any other bonus already granted by its enchantment.

Spellbound weapons are treated as attuned equipment, and obey all other rules of attuned items, even if they are otherwise non-magical. You may spellbind as many weapons as you have free attunement slots for.

Arcane Infusion

Starting at 3rd level, you can use an action to imbue a non-magical weapon you are spellbound to with elemental energy, temporeraly granting it a magical element of your choice from the following: fire, cold, lightning, thunder, acid, or necrotic.
This temporary enchantment lasts for 1 minute, and will persist even if the weapon is dropped or thrown.
While infused with this trait, the weapon will deal an extra 1d4 bonus damage of the infused type in addition to its base damage. This bonus increases to 1d6 at 5th level, 1d8 at 10th level, and 1d10 at 15th level.
You can use this feature a number of times equal to your Intelligence modifier (minimum of 1 time).
The use of this feature will refresh after a short or long rest.
This trait cannot be applied to magical weapons.
You can use a bonus action to finish the Arcane Infusion early, if you so choose.

Elemental Link

After reaching 7th level, during each long rest, you may choose to link with one of the following elements: fire, cold, lightning, thunder, acid, or necrotic.
While linked to that element you gain resistance to all damage of its type.
In addition, when you use Arcane Infusion with your linked element, the dice you roll for the elemental damage is doubled for that element. For example, if you would normally roll a 1d8, you roll 2d8 instead.

Empowered Strike

At 10th level, when you are wielding a weapon enhanced by Arcane Infusion, you may use a bonus action to grant it a special attribute on your next attack. If the attack lands, the target suffers an effect related to the infused element, as listed below. If the attack misses, the effect is lost.

Certain effects can be bolstered if you are linked to their element via Elemental Link.

Intelligence is your modifier when determining the spell save DC for the following effects:

• Fire: The target is set on fire for 1 minute. It suffers 1d6 points of fire damage at the start of each of its turns. The target can put out the fire if it spends an action on its turn to extinguish the flames. If you are linked to this element, the target must succeed on a Dexterity saving throw against your spell save DC to succesfully put out the flames as an action on its turn.

• Cold: The target loses 10 feet of its total walking speed for a number of rounds equal to your Intelligence modifier (Minimum of 1 round). If you are linked to this element, the target also has disadvantage on Dexterity saving throws and Attack Rolls while the effect lasts.

• Lightning: All hostile creatures within 10 feet must succeed on a Dexterity saving throw or also receive the lightning damage granted by Arcane Infusion. If you are linked to this element, this effect's range is expanded to 15 feet, and the targets will still take half damage on a succesful save.

• Thunder: If the target is Large or smaller, it is pushed back 10 feet and must succeed on a Constitution saving throw against your spell save DC or be knocked prone. If you are linked to this element, you can affect up to Huge creatures, pushing them up to 20 feet and any creature of the same size or smaller on the path of the target as it is pushed must succeed on a Dexterity saving throw against your spell save DC or be knocked prone as well.

• Acid: The target's maximum hit points are reduced by half of the attack's total damage until the next dawn. If you are linked to this element, attacks against the target have advantage until the end of your next turn.

• Necrotic: You leech life from the target equal to half the total damage dealt by the attack. If you are linked to this element, you have advantage on the attack roll to land this attack and leech the full amount of damage dealt to the target.

You can use this feature once each time you have Arcane Infusion active. The number of uses increases to two at 15th level.

True Infusion

After you gain this feature at 15th level, you become capable of unleashing your full latent arcane power through Arcane Infusion. Throughout its 1 minute duration, you may switch the infused element as a bonus action without the use of another infusion, and each time you land a critical hit, or deal a finishing blow on a target, you gain an additional use of Empowered Strike for the duration of that Arcane Infusion.

Arcane Aura

At 18th level, while using Arcane Infusion, you emit a small aura of any actively infused element's type. When a creature lands a melee attack against you, you may use your reaction to lash out with your infused element, dealing 2d10 + your Intelligence modifier in damage of that element's type to all creatures you choose within 5 feet of you. You may use this feature once each time you use Arcane Infusion.