Your body transforms entirely into magical resonant metal for the duration. Choose one damage type out of bludgeoning, piercing, slashing, or thunder. You gain the following benefits while transformed:

• You are immune to thunder damage and you have resistance to all damage except lightning damage.
• You ignore the effects of disease, exhaustion, and poisons. Any poisons or diseases already in your system are suspended, not neutralized.
• You gain a +2 bonus to AC, and your AC can't be less than 18, regardless of what armor you are wearing.
• You are five times as loud, and any creature that sees you can hear you as if you were only 10 feet away.
• You are immune to the silence and howling void spells, and to the effects of being in an environment with high or low pressure. You cannot be prevented from speaking or providing verbal components.
• When a spell you cast deals damage of the chosen type, it ignores resistance to that damage type, and it deals extra damage of that type equal to 10 + twice the spell's level. A spell can't deal this extra damage to any creature more than once per turn.