The Grass Jelly Dimension is a parallel dimension within the Multiverse. It contains multi-sided cubes containing spheres of multi-colored light. It is one of the first dimensions that Doctor Stephen Strange was exposed to during his first journey through the Multiverse.
The Grass Jelly Dimension is a vast reality that contains a seemingly endless number of icosahedron-like cubes floating in space. Each cube contains a sphere of light which radiates bright multi-colors. The cubes are transparent and have a green-blue tint to them as a result of the light within them. As a result, the dimension, which is void of other sources of light, has a green-blue glow to it. The spheres of light can take on a cube-like appearance due to the shape of their containment. As they floated in space, the cubes would rotate, causing the number of their sides to alternate. The dimension is uninhabitable and can only be visited in astral form.
Stephen Strange traveled to the Grass Jelly Dimension when the Ancient One sent him on a journey throughout the Multiverse. After experiencing the terrifying reality of the Mandelibus Dimension, Strange entered the Grass Jelly Dimension after passing through a crystal prism-like dimension. Strange floated through the silent void and looked about with a look of astonishment as he took in his surroundings. As he floated, he was unaware that he was approaching one of the floating cubes. Turning, he saw the cube started to shift and fractal in on itself. The shifting cube then opened into a gateway which drew Strange screaming into the Dark Dimension.