Gish

A revamp on the Eldritch Knight, bringing it on par with later released subclasses. 
More flexibility and variety.

Gish Knight Spellcasting

The Gish Knight is a third-caster. You can use the Eldritch Knight Spellcasting Table for spells known and spells slots.

Spellcasting

When you reach 3rd level, you augment your martial prowess with the ability to cast spells.

You choose one spell list from the following classes: Bard, Cleric, Druid, Sorcerer or Wizard. Your spellcasting ability is the same of the respective class.

Cantrips

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

Spell Slots

The Gish Knight Spellcasting table shows how many spell slots you have to cast your 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  spells of your choice from the chosen spell list

The Spells Known column of the Gish Knight Spellcasting table shows when you learn more spells of 1st level or higher. Each of these spells 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 spell list.

Whenever you gain a level in this class, you can replace one of the spells you know with another spell of your choice from the chose spell list. The new spell must be of a level for which you have spell slots.

Spellcasting Ability

Your spellcasting ability for your spells depends on which spell list you chose. You use your that ability whenever a spell refers to your spellcasting ability. In addition, you use the same ability modifier when setting the saving throw DC for a  spell you cast and when making an attack roll with one.

Bard, Sorcerer = Charisma 

Cleric, Druid = Wisdom

Wizard = Intelligence

Spell save DC = 8 + your proficiency bonus + your spell casting ability modifier

Spell attack modifier = your proficiency bonus + your spell casting ability modifier

Gish Weapon

At 3rd level, you learn a ritual that creates a magical bond between yourself and one weapon. You perform the ritual over the course of 1 hour, which can be done during a short rest. The weapon must be within your reach throughout the ritual, at the conclusion of which you touch the weapon and forge the bond.

Once you have bonded a weapon to yourself, when you attack with that weapon, you can use your spell casting ability modifier, instead of Strength or Dexterity, for the attack and damage rolls.  If it is on the same plane of existence, you can summon that weapon as a bonus action on your turn, causing it to teleport instantly to your hand. You can use the bonded weapon as a spellcasting focus. The weapon is considered magical for the purpose of overcoming resistances.

If you attempt to bond with a another weapon, you must break the bond with the one you are bonded with.

Gish Attack

Starting at 7th level, when you take the attack action, you can cast one of your cantrips in place of one of your attacks.

Gish Defense

At 10th level you learn the Shield  and Absorb Elements spells, if you do not already know them. These spells count as a gish spells for you, but they don’t count against the number of spells you know. These spells can’t be replaced when you gain a level in this class. You can cast each of the spells once without spending a spell slot.

Gish Mobility

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 or Second Wind. You can teleport before or after the use of any of these features.

Gish Prowess

At 18th level once per day you can cast a spell that takes an action as a bonus action. If the spell requires concentration, you have advantage on concentration checks to maintain it.