You belong to a subrace of Tortles capable of emerging from their shells.  During a short or long rest you can leave your shell.  While you are outside of a shell your body is pale and vulnerable. Your base AC is 10 + Dexterity modifier, and you have disadvantage on Strength and Constitution saving throws while outside your shell.

Due to the shape of your body, you are still ill-suited to wearing armor like all Tortles. A Common Shell provides ample protection, however; it gives you a base AC of 17 (your Dexterity modifier doesn’t affect this number). You gain no benefit from wearing armor, but if you are using a shield, you can apply the shield’s bonus as normal. 

Additionally, you have access to a new Downtime Activity, Seek Shell which can allow you to find shells with various properties.  The rarity of a shell is the same as that armor with the same property.  For instance:

• An Uncommon Shell could have the properties of Mariner's Armor, Adamantine Armor, or any other Uncommon armor .
• A Rare Shell could have the properties of Armor, +1, Armor of Resistance, or any other Rare armor.
• A Very Rare Shell could have the properties of Armor, +2, Dwarven Plate, or any other Rare armor.
• A Legendary Shell could have the properties of Armor, +3, Armor of Invulnerability, or any other Legendary armor.

Seek Shell

Finding a new shell requires time and money to seek out. Even then, there is no guarantee you will find the type of shell you seek.

Resources. Finding a new shell requires at least one workweek of effort and 100 gp in expenses. Spending more time and money increases your chance of finding a high-quality shell.

Resolution. A Hermit Crab seeking a new shell makes a Wisdom(Survival) check to determine the quality of the seller found.  The  a +1 bonus on the check for every workweek beyond the first that is spent seeking a shell and a +1 bonus for every additional 100 gp spent on the search, up to a maximum bonus of +10. 

Use the table below when seeking a new shell. The DM has the final say in determining which shells are for available and the final price, no matter what the table says. The DM may also allow a Hermit Crab to seek a specific type of shell using this table or roll randomly.