This is a test sub class! Feel free to use it and playtest. Comment on how it can be improved!

Spellcasting

When you reach 3rd level, you augment your martial prowess with the ability to cast spells. See Spell Rules for the general rules of spellcasting and the Spells List for the wizard spell list.

Cantrips

You learn two cantrips of your choice from the wizard spell list. You learn an additional wizard cantrip of your choice at 10th level.

Spell Slots

The Mystic Knight Spellcasting table shows how many spell slots you have to cast your wizard spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell’s level or higher. You regain all expended spell slots when you finish a long rest.

For example, if you know the 1st-level spell shield and have a 1st-level and a 2nd-level spell slot available, you can cast shield using either slot.

Spells Known of 1st-Level and Higher

You know three 1st-level wizard spells of your choice, two of which you must choose from the abjuration and evocation spells on the wizard spell list.

The Spells Known column of the Mystic Knight Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an abjuration or evocation spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.

The spells you learn at 8th, 14th, and 20th level can come from any school of magic.

Whenever you gain a level in this class, you can replace one of the wizard spells you know with another spell of your choice from the wizard spell list. The new spell must be of a level for which you have spell slots, and it must be an abjuration or evocation spell, unless you’re replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.

Spellcasting Ability

Intelligence is your spellcasting ability for your wizard spells, since you learn your spells through study and memorization. You use your Intelligence whenever a spell refers to your spellcasting ability. In addition, you use your Intelligence modifier when setting the saving throw DC for a wizard spell you cast and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your Intelligence modifier

Spell attack modifier = your proficiency bonus + your Intelligence modifier

Mystic Knight Spellcasting

Fighter Level	Cantrips Known	Spells Known	— Spell Slots per Spell Level —
			1st	2nd	3rd	4th
3rd	2	3	2	—	—	—
4th	2	4	3	—	—	—
5th	2	4	3	—	—	—
6th	2	4	3	—	—	—
7th	2	5	4	2	—	—
8th	2	6	4	2	—	—
9th	2	6	4	2	—	—
10th	3	7	4	3	—	—
11th	3	8	4	3	—	—
12th	3	8	4	3	—	—
13th	3	9	4	3	2	—
14th	3	10	4	3	2	—
15th	3	10	4	3	2	—
16th	3	11	4	3	3	—
17th	3	11	4	3	3	—
18th	3	11	4	3	3	—
19th	3	12	4	3	3	1
20th	3	13	4	3	3	1

Magick Infusions

At 3rd level, you learn to imbue elemental energy into your weapon. Choose one Infusion from the Infusion table.

As a bonus action, you can activate an enchantment on a single weapon with the elemental energy of a known Infusion of your choice that lasts until you finish a short or long rest.

For the duration, attacks from this weapon deal an additional 1d4 damage of the chosen enchantment type. This damage is magical, and increases as you gain levels as a mystic knight. A weapon can only hold a single active enchantment at a time.

You learn an additional an additional infusion at 7th level and another at 11th level.

You can use this feature twice, you must finish a short or long rest before you can use it again. Starting at 11th level, you gain an one additional use.

At Higher levels: The damage increases to 1d6 at 7th level and 1d8 at 11th level. 

Magick Riposte

Beginng at 7th level, whenever you use the Magick Infusion feature, the effect now also applies to your shield. Upon being hit, you may use your reaction to intercept the incoming attack with your shield releasing the energy stored towards the attacker. The energy then dissipates from the shield. 

While infused, shield glows with the imbued elemental energy casting 10 feet of dim light.

Flame Riposte (Ingle)

When you riposte, a torrent of flame comes spewing back at the attacker. The creature must make a dexterity saving throw. It takes 3d10 fire damage on a failed save, or half as much on a successful one. On a failed save, the creature lights on fire dealing 1d4 fire damage at the beginning of each of its turns.

Ice Riposte (Frazil)

When you riposte, a shroud of ice entombs the attacking creature. The creature must make a constitution saving throw or be incased in ice, reducing movement speed to 0. The creature is considered restrained and may make a Strength check to break free on the beginning of each of its turns.

Lightning Riposte (Levin)

When you riposte, a stroke of lightning forming a line of 30 feet and 5 feet wide blasts out from in front of you in a straight line. Each creature in the line must make a Dexterity saving throw. A creature takes 4d6 lightning damage on a failed save, or half as much on a successful one.

Blessed Riposte (Holy)

When you riposte, a bright light bursts forth from the shield. All enemy creatures within a 10 foot cone in front of you must make a constitution saving throw or be blinded for 1 minute. The effect does nothing on a successful save.

Abyssal Riposte (Sopor)

When you riposte, three dark tentacles come lashing out at the attacker dealing 3d10 necrotic damage. You heal yourself half the damage dealt.

Thunder Riposte (Brontide)

When you riposte, a thundering blast bursts forth around you knocking back your enemy. Creatures within a 10 foot radius must make a Strength saving roll or be pushed back 10 feet. On a failed save, the creatures are also knocked prone. The sound made can be heard within 300 feet.

Saving Throws. Some of your riposte require your target to make a saving throw to resist the riposte effects. The saving throw DC is calculated as follows:

Riposte save DC = 8 + your proficiency bonus + your Intelligence modifier

Infusions

Infusions are listed in alphabetical order.

Abyssal Infusion

Your infusion damage is now necrotic damage.

Brontide Infusion

Your infusion damage is now thunder damage.

Frazil Infusion

Your infusion damage is now cold damage.

Holy Infusion

Your infusion damage is now radiant damage.

Ingle Infusion

Your infusion damage is fire damage. 

Levin Infusion

Your infusion damage is now lightning damage.

Magick Might

At 10th level, you learn how to make your weapon strikes undercut a creature’s resistance to your spells. When you hit a creature with a weapon attack, that creature has disadvantage on the next saving throw it makes against a spell you cast before the end of your next turn.

Magick Surge

At 15th level, you gain the ability to teleport up to 30 feet to an unoccupied space you can see when you use your Action Surge. You can teleport before or after the additional action.

Improved Magick Infusion

Starting at 18th level, you have mastered the magick arts. You gain two additional uses of the Magick Infusion feature, which can be used to enchant your weapon with two enchantments.

Each subsequent enchantment must use an additional point. 

If you start combat with no Infusion points you gain two at the beginning of combat.