Source: Unearthed Arcana 38 - Feats for Skills

You become more nimble, gaining the following benefits:

• Increase your Dexterity score by 1, to a maximum of 20.

• You gain proficiency in the Acrobatics skill. If you are already proficient in the skill, you add double your proficiency bonus to checks you make with it.

• As a bonus action, you can make a DC 15 Dexterity (Acrobatics) check. If you succeed, difficult terrain doesn’t cost you extra movement until the end of the current turn.