There might not be a more difficult profession than the creation of magical items. A competent enchanter could spend months or years crafting a single item, painstakingly ensuring every single detail was perfect.

The Rune Knight has no such time for that. They have studied the glyphs and runes used by enchanters, and created an 'abridged' version of it. A wizard would look at their work and call it 'nearly incomprehensible nonsense', but the Rune Knight can use the faint glimmer of arcane talent in them to draw power from their Runic Inscriptions, and combine it with their martial prowess to create a weapon of immense potential power- The Runeblade. 

Made with great cost and care, the Rune Knight is little more than an average warrior without their chosen instrument in hand. However, if you ever see a fighter that wields a blade lined with glowing runes, flight might be your best option.

Runeblade

At 3rd level, you have learned how to transform any melee weapon into a Runeblade. By spending 4 uninterrupted hours, you can inscribe a weapon with magical runes and gems that allow you to channel certain energy through contact. This requires you to use Jeweler's Tools as well as an amount of gems and powdered silver equal to 4 x the weapon's value, which are consumed in the process. Once a weapon has been transformed into a Runeblade, it cannot be undone.

In addition, because they are imperfect enchantments, only a Rune Knight can activate the Runic Inscriptions. When any creature who isn't a Rune Knight attempts to wield a Runeblade, the Runic Inscriptions become inert.

When you create a Runeblade, it is only with the Runic Inscriptions you know at the time. If you gain new Runic Inscriptions after creating a Runeblade, you must repeat the transformation process on that weapon to be able to use the new Inscriptions.

Weapons that are already enchanted can also be transformed into a Runeblade without disrupting the previous enchantment, however, the GM may impose an Arcana skill check if the selected weapon has a particularly powerful or ancient enchantment. On a failed check, the previous enchantment is permanently lost.

The Runeblade always requires attunement, even if the original weapon did not. If the original weapon previously required attunement, then it will instead use two attunement slots after it has become a Runeblade. If an existing enchanment is lost during the process of creating a Runeblade, any previous requirements of attunement are also removed from the weapon.

In addition, you also gain proficiency with Jeweler's Tools and Arcana.

Edge of Arcana

At 3rd level, you have learned how to inscribe a set of runes that channel certain schools of magic through your blade, and activate them in the heat of battle.

Choose two of the Runic Inscriptions below. These will comprise the totality of your enchantment. You gain knowledge of additional Runic Inscriptions at 6th, 14th and 18th levels.

As a bonus action, you may activate one of the Runic Inscriptions on the Runeblade you wield to receive the associated enchantment. The enchantment lasts for 1 minute, and if there was already an active Runic Inscription, then replace the previous one with the newly selected enchantment. 

In addition, attacks with your Runeblade while a Runic Inscription is active are considered magical for the purposes of damage resistance against non-magical attacks.

 

Blessed Blade

This weapon hums with divine light, and almost seems to move of its own accord. Whenever you make a melee weapon attack with the Runeblade, roll 2d4 and add one of the results to your attack roll.

Brilliant Blade

Light reflects strangely off your Runeblade while this enchantment is active, refracting into a spectrum of colors at different angles. Whenever you miss with a melee weapon attack with your Runeblade, the creature that you targeted with the attack must make a wisdom saving throw. If they fail, roll 4d10. If the creature's current hit point total is less than the total amount rolled, then the creature becomes blinded until the end of your next turn.

The difficulty class for the saving throw is 8 + your proficiency bonus + your intelligence modifier.

Chromatic Carve

The glowing runes across your weapon hum brightly, changing color with each pulse. Whenever you use the Attack action, select a damage type: acid, cold, fire, lightning, poison, or thunder. Until the end of your turn, add 1d6 of the selected damage type to each successful weapon attack with your Runeblade.

At 11th level, the damage die for this ability becomes 1d8. At 17th level, it becomes 1d10.

Coiling Chains

A thin, pitch-black chain churns and wraps around your weapon while this enchantment is active. Whenever you take the Attack action, you may forego 1 attack to instead attempt to bind an enemy with the chain. Choose a creature within 5 ft. of you. That creature must make a Strength saving throw or become Restrained until the start of your next turn. You cannot use this ability if a creature is already restrained by this effect. The creature may use an Action to repeat the saving throw during their turn. If they succeed, the effect ends.

The difficulty class of the saving throw is 8 + your proficiency bonus + your intelligence modifier.

Displacer Drive

Time itself seems to bend around your Runeblade when this enchantment is active, temporarily slowing those that are struck by it. Creatures that take damage from your Runeblade lose -1 AC and cannot take Reactions until the beginning of their next turn. A creature cannot be affected by this ability more than once at a time.

Reaping Rake

Foul energies and an unnatural coldness seep from your weapon while this enchantment is active. Whenever you make a successful melee weapon attack, gain hit points equal to half of the total physical weapon damage dealt (rounded down).

Shimmering Swipe

With every swing of your weapon, faint barriers are woven behind it. Each time you make a melee weapon attack with your Runeblade that hits, gain +1 AC until the beginning of your next turn.

Spell Sunder

At 7th level, you gain the ability to disrupt hostile magics with your Runeblade. When you are targeted by a spell cast by a hostile creature, you can use your Reaction to attempt to sunder it. Make an attack roll with your Runeblade to match or exceed the spell's AC, calculated below. If the attack is successful, you avoid all effects of the spell.

The AC of the triggering spell is 14 + the level of spell slot used to cast the spell.

If you roll a 20 on the die for your Spell Sunder attack roll, then you also capture the spell, gaining 1 charge. Whenever you make an attack roll that hits, you may expend the charge and release the captured spell against the creature being attacked. That creature receives the effects of the spell that was sundered as if they had been targeted by it. Any necessary calculations are made using the statistics of the original caster, and if the spell's duration was concentration, then the duration is 1 round instead.

Charges gained by capturing a sundered spell are lost after 1 minute.

Once you have used this ability, it cannot be used again until you complete a short or long rest.

Overflowing Power

At 11th level, you learn how to intensify the power of your runic enchantments when it counts. 

When you make a melee attack roll using a Runeblade with one or more active enchantments, you can expend 1 Extra Attack to empower the enchantment(s).

If dice are rolled as part of the enchantment's effects, roll twice as many dice and use twice as many results. If a saving throw is made as part of the enchantment's effects, it is made at disadvantage. If armor class is affected as part of the enchantment's effects, double the amount.

Rune Master

Starting at 15th level, your mastery of the Runeblade allows you to have two enchantments active at once, instead of one. 

If you attempt to activate a 3rd enchantment while two are already active, you can choose which of the current enchantments to replace.