Arcane Warrior: Aegis

While most arcane warriors who engage in melee combat prefer to have a free hand for spell-weaving, or to wield two-handed weapons, some mage-knights learn to augment their defenses with a magic-infused shield, making themselves especially resilient on the battlefeld. This is the path of the Aegis. These arcane warriors learn to weave magic while handling shields so as to protect themselves and their comrades. Though they are able to take an incredible amount of punishment, only a fool would think the aegis incapable of striking back with surges of magic, retaliating against anyone fool enough to try and break them.

Spellshield

3rd-level Aegis feature
As an aegis, you have further mastered martial disciplines to allow you to always be prepared to defend yourself. If you have a free hand and are not wearing a shield, you can conjure a shield in your hand as a part of any ability you use that uses your reaction or bonus action. This conjured shield remains until you doff it or dismiss it (no action required).

Alternatively, you can perform a magic ritual that creates a bond between you and a magic shield over the course of 1 hour, which can be done during a short rest. The shield must be within your reach throughout the ritual, at the conclusion of which you touch the shield and forge the bond. A shield you bond with can be summoned and dismissed the same way as the conjured shield. While it is dismissed, it disappears, but you remain attuned to it.

You can't be disarmed of shields you conjure or are bonded with, nor can such shields be destroyed.

Shield of the Aegis

3rd-level Aegis feature
Starting when you select this tradition at 3rd level, you can reduce the impact of incoming attacks. Whenever you are hit by an attack while wielding a shield and while benefiting from your Arcane Deflection ability, you can expend 2 mana to reduce the damage you take by an amount equal to your Intelligence modifier (minimum 1) plus your shield's AC bonus.

Absorbing Shield

7th-level Aegis feature
Starting at 7th level, you have learned how to absorb energy with your shield. Whenever you take acid, cold, fire, lightning, or thunder damage while holding a shield, you can use your reaction and spend 3 mana to gain resistance to the triggering damage type as long as you aren't incapacitated. You retain this resistance as long as you are holding your shield or until you use this ability again.

If you have the Shield Master feat, you may activate this ability as a part of the same reaction.

Retributive Shield

11th-level Aegis feature
Beginning at 11th level, attacking you becomes dangerous. Whenever a creature misses you with a melee attack while you're wielding a shield, you can use your reaction and expend 2 mana to blast the attacker with energy. The attacker takes 2d8 force damage and must make a Strength saving throw against your spell save DC. On a failed save, the creature is either pushed 10 feet away from you or knocked prone (your choice).

If using your Arcane Deflection ability caused the attack to miss, you may activate this ability as a part of the same reaction.

Improved Retributive Shield

15th-level Aegis feature
Starting at 15th level, whenever a creature misses you with a melee attack while you're wielding a shield and are not incapacitated, that creature takes force damage equal to your Intelligence modifier (minimum 1).

If you have used your Retributive Shield reaction since your last turn, this force damage increases by 1d8.