Base Class: Wizard
Wizards who have devoted themselves to the principals of Abjuration magic, but not focusing on it's entirety. Wizards who are known as Defense Mages have specialized in making barriers to protect themselves, their allies, and structures around them.
(Another Dust subclass! This subclass is SUPER busted. I threw balancing out the window and decided to make a subclass that fulfilled my fantasies. Probably going to be a recurring thing in my subclasses, classes, and feats. Also kinda made this subclass during a school night and didn't sleep ;-; This is just a souped up Abjuration Wizard. DMs beware because of how unpolished and broken this subclass is.)
Defensive Aid
Starting at 2nd level, your keen ability to assess tactical situations allows you to act quickly when on the defensive. You gain a number of Reactions equal to half your Proficiency Bonus (rounded up). These additional Reactions may only be used to use Defense Magic abilities or to cast an Abjuration spell. Additionally, you may use a Reaction to send a piece of your Arcane Ward to protect an ally, which it can reduce damage up to fives times your Proficiency Bonus. Any remaining hit points the Arcane Ward has when used this way returns to your main Arcane Ward.
Arcane Ward
Starting at 2nd level, you can weave magic around yourself for protection. When you cast an abjuration spell of 1st level or higher, you can simultaneously use a strand of the spell’s magic to create a magical ward on yourself that lasts until you finish a long rest. The ward has a hit point maximum equal to 5 times your wizard level, Intelligence modifier and Proficiency Bonus. Whenever you take damage, the ward takes the damage instead. If this damage reduces the ward to 0 hit points, you take any remaining damage.
While the ward has 0 hit points, it can’t absorb damage, but its magic remains. Whenever you cast an abjuration spell of 1st level or higher, the ward regains a number of hit points equal to five times the level of the spell.
Once you create the ward, you can’t create it again until you finish a long rest.
Defensive Domain
Starting at 6th level, magic barriers you weave into existence are your domain of absolute defense.
Your Arcane Ward now effects creatures or structures you designate within 10 feet of you. When using Arcane Ward like this, you do not need to expend a Reaction to use Defensive Aid and the damage reduction is no longer limited to your Proficiency Bonus times five. Additionally, creatures you choose within your Arcane Ward are also effected by the Shield spell when you cast it, but they instead only add half your Proficiency Bonus (rounded down).
At 10th level, the range of the Arcane Ward increases to 15 feet and at 14th level, it increases to 20 feet.
Absolute Defense
Starting at 10th level, your arcane barriers have grown to a level where they can ward off anything. Creatures within your Arcane Ward gain a bonus to saving throws equal to you Proficiency Bonus.
Arcane Fortress
Starting at 14th level, your enemies struggle to even close the distance. Your Arcane Ward now counts as solid terrain. A creature may not move into the space of your Arcane Ward through any means besides teleportation or walking through a tear in the Arcane Ward. You may choose what is allowed to enter your Arcane Ward.
When your Arcane Ward is to receive damage equal to three times your Proficiency Bonus in one turn, a small tear opens within the barrier which only stays open for that turn. Even when the Arcane Ward has a tear, you and your allies gain the benefits of being within the Arcane Ward.
Attacks against the Arcane Ward from the outside are considered to have resistance until a tear is formed.
When moving into a creature while using your Arcane Ward like this, your Arcane stops moving with you. If you exit your Arcane Ward, your Arcane Ward shrinks down to it's normal size. You may also choose to change the size of your Arcane Ward at will, but it can't exceed 20 feet.