Duo-dimesion

Your form collapses in on itself, leaving you with only two dimensions: height and width, with no depth. As a duo-dimensional wizard, you can pass through the thinnest of spaces as long as the space has the proper height. For example, you can squeeze through the space between a door and its frame without any trouble. While two-dimensional, you perform actions normally. As a bonus action, you can turn sideways to disappear, detectable only with a true seeing spell or similar method. While invisible, you can not be affected by any form of attack nor can you make attacks, interact with objects, or cast spells. However, when you are visible, you are subject to double the normal amount of damage from attacks as if hit by a critical hit.