A Mask is an object that can only exist as a child of a Clip Group object and acts as an opacity mask for that particular clip group. Unlike Clip Path, Mask allow gradual fading and soft edges and can be constructed from both raster and vector images.
Properties
The following properties are available for Mask objects:
Compositing
Blend modes and opacity
Transform
Scale, rotate, skew, and other affine transformations
Coordinates
Global coordinates and size
Specific properties
Mask objects don't have specific properties.