a crystal ball; and

a support seat, the support seat being provided with a bearing portion, and a bearing recess and a mounting opening being provided in the top of the bearing portion, wherein the bearing recess allows insertion of at least part of a lower portion of the crystal ball to bear the crystal ball, and the mounting opening is located at the top of the bearing recess, is in communication with the bearing recess, and allows at least part of the lower portion of the crystal ball to enter and exit the bearing recess vertically; and the support seat having a mounting hole running through the support seat from front to rear, wherein the mounting hole is located above the bearing recess, is in communication with the bearing recess via the mounting opening, and receives a remaining portion of the crystal ball exposed from the bearing recess, a distance between a hole wall part of the mounting hole at the highest point and the mounting opening being smaller than a diameter of the crystal ball.