When you take the Attack action on your turn, you can replace one of your attacks with an exhalation of magical energy in either a 15-foot Cone or a 30-foot Line that is 5 feet wide (choose the shape each time). Each creature in that area must make a Dexterity saving throw (DC 8 plus your Constitution modifier and Proficiency Bonus). On a failed save, a creature takes 1d10 fire damage. On a successful save, a creature takes half as much damage. This damage increases by 1d10 when you reach character levels 5 (2d10), 11 (3d10), and 17 (4d10).

You can use this Steam Breath Weapon a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.

You have Resistance to fire damage granted from your dragon turtle ancestry.

You have Darkvision with a range of 60 feet.

You have Advantage on any ability check you make to end the Grappled condition. You also count as one size larger when determining your carrying capacity.

You can hold your breath for up to 1 hour

While your size and anatomy does not allow dragon tortles to retreat within their shells, your shell and armored hide provides significant protection giving you a base AC of 17 (your DEX modifier doesn't affect this number). You can’t wear light, medium, or heavy armor, but can continue using and applying a shield’s bonus as normal.