Unbreakable Resolve

As a reaction after suffering a dire hit, you may call upon powerful instinctual resolve that you draw from the powerful, unerring magic inside of you. For the duration, you emit an awesomely powerful magical radiance displaying impeccable levels of power, granting you the following benefits:

• Your armor class increases by 15, and all attack rolls against you have disadvantage.
• You have advantage on all saving throws. You can also replace the roll with a 17, should you roll any lower.
• Whenever you make an attack roll, you can add a bonus equal to half your spellcasting ability score, rounded down.
• You have advantage on all attack rolls, and creatures have disadvantage on saving throws caused by your attacks and spells.
• As a bonus action on each of your turns, you can teleport up to 120 feet to an unoccupied space that you can see.
• Whenever a creature starts its turn within 5 feet of you or enters that radius for the first time on its turn, it must make a Constitution saving throw, taking 10d4 radiant damage on a failed save, or half as much on a successful one.
• You are immune to becoming charmed, frightened, grappled, incapacitated, paralyzed, petrified, poisoned, prone, restrained, and stunned, and you are unaffected by the magic missile spell.
• Whenever you cast a spell that deals damage, you add your proficiency bonus to the number of damage dice you roll. If the spell does multiple damage types at once, you may distribute the dice to each damage type as you wish.

The effect ends when your concentration is broken, when you regain hit points, or when you sustain damage. When the spell ends, a wave of immense physical fatigue instantly overwhelms your body. You suffer two levels of exhaustion and immediately enter death saves.