Contortionist

Through natural ability or arduous training, you have honed your body to be flexible beyond the ability of most.  You are able to bend and contort your body in astonishing ways:

• Increase Dexterity by 1, to a maximum of 20.
• You gain proficiency in Acrobatics.
• .You are able to contort, twist, bend and compress yourself into spaces too small for someone of your Size.  As a Bonus Action, you can temporarily reduce your Size by one and can move through spaces occupied by beings your normal Size or larger.  Your encumbrance modifiers, carrying capacity and your movement speed does not change.  You can hold this new contorted shape for a number of rounds equal to 1 + your Constitution modifier (minimum of 2) before you need to make a Constitution saving throw.
• You gain advantage on Dexterity (Acrobatics) checks to break a grapple.