Augustric Battlemagic (True Homebrew)

This unorthodox magical tradition originates from the techniques passed down by an ancient and incredibly influential wizard prodigy known as Augustrum, who used his understanding of matter and energy to wield a Greatsword as if it were a weapon half its weight, and to seamlessly use it in conjunction with spellcasting. This is a very secretive tradition known only by few, and such circles are not the type to freely give away these secrets.

Greatsword Imbuement

When you adopt this tradition at 2nd level, you learn a ritual that creates a magical bond between yourself and a greatsword. You perform the ritual over the course of 1 hour, which can be done during a short rest. The greatsword must be within your reach throughout the ritual, at the conclusion of which you touch it and forge the bond. Once the bonding ritual is complete, the Greatsword becomes bound to you: while you are wielding it, it counts as a magical weapon, loses the Two-Handed and Heavy properties, and gains the Finesse property. You can't be disarmed of the Greatsword unless you are incapacitated. 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. Lastly, you can use the Greatsword as your Spellcasting focus.
You can have only one bonded Greatsword at a time. If you attempt to bond with another greatsword, it breaks the bond to your current one.

Spell Strike

Starting at 2nd level, you can use an action on your turn to attempt a spell strike, concentrating a spell into your Greatsword and using the strike to cast it onto a target. Choose a spell you know of 1st level or higher with a casting time of one action, and spend a spell slot as if you were casting it as normal. The spell must be capable of targeting a hostile creature or have an are of effect in the shape of a cone, cube, cylinder, line, or sphere. As part of the action, you then make a single weapon attack with your bonded Greatsword. If the attack hits, the target suffers the attack’s normal effects and the effects of the spell. The target has disadvantage on all saving throws made against the spell (if any), and automatically fails dexterity saving throws. If the spell is area of effect, it instead only affects the target. Whether the weapon attack hits or misses, the spell slot is expended and the magic fades from the blade.

Recursive Strike

At 6th level, after you use your Spell Strike feature, you can immediately make a single weapon attack against the same target as a bonus action. If the Spell Strike missed, you can attempt another Spell Strike identical to the first one with this bonus action attack before the magic fades from the weapon.

Magic Ward

Beginning at 10th level, while wielding your bonded Greatsword, your AC increases by 2. Additionally, whenever you start combat and have your bonded Greatsword equipped, you gain temporary hit points equal to twice your wizard level.

Limbo Blade

Beginning at 14th level, melee weapon attacks you make with your bonded Greatsword deal an additional amount of damage equal to your wizard level. You can choose for this damage to be one of the following when making the attack: force, fire, cold, lightning, acid, poison, radiant, or necrotic. Additionally, if you or an ally are hit by a weapon attack from a creature within 120 feet of you that you can see, you can use your reaction to teleport and reappear in a spot within 5 feet of the attacker. You can then immediately make a weapon attack with your bonded Greatsword against that creature as part of this reaction. You may use this ability a number of times equal to your proficiency bonus, and regain all expended uses of this ability when you finish a long rest.

At level 20, once per short or long rest, you may replace the weapon attack included in the reaction with a spell strike.