Shell Defense

You can withdraw into your shell as an action.
Until you emerge, you gain a +4 bonus to your
AC, and you have advantage on Strength and Constitution saving throws. While in your shell,
you are prone, your speed is 0 and can't increase,
you have disadvantage on Dexterity saving
throws, you can't take reactions, and the only
action you can take is a bonus action to emerge
from your shell.