Aoanna's Thunderous Form

You empower yourself with thunderous might fuelled by magic. Until the spell ends, you can’t cast spells, and you gain the following benefits:

• You gain resistance to non-magical bludgeoning, piercing, slashing, fire, cold, and thunder damage. 
• You have advantage on attack rolls that you make with unarmed strikes.
• When you hit a target with an Unarmed Strike, that target takes an extra 2d12 Thunder damage.
• You have a strength score of 18, this remains unchanged if your strength score is higher than 18.
• You gain +2 to your armour class.
• You have proficiency in Strength saving throws.
• You can attack twice, instead of once, when you take the Attack action on your turn. You ignore this benefit if you already have a feature, like Extra Attack, that gives you extra attacks.
• You can cast the thunder step spell as part of the attack action once per turn.

Immediately after the spell ends, you must succeed on a DC 15 Constitution saving throw or suffer one level of exhaustion.