The Skewb Diamond is an octahedron-shaped puzzle and a fairly straight-forward variant of the Skewb. Since the Skewb is a cube-shaped puzzle, and the octahedron is the dual of the cube, it follows that the Skewb Diamond is simply a Skewb in which corner pieces have been exchanged for face pieces, and vice versa. This introduces a slight change in the nature of the puzzle, since corner pieces must be oriented correctly, whereas face pieces do not. Aside from this, the Skewb Diamond is essentially a Skewb.
The Skewb Diamond belongs to the family of Skewb variants which also includes the Skewb itself, the Skewb Kite, the Skewb Ultimate, and the Tetrakaidecahedron. The last of these is in the shape of a truncated octahedron, and is essentially a Skewb Diamond with the vertices cut off. In terms of play it is identical.