Remix of a derivative of https://www.thingiverse.com/thing:2839354
Someone else added vertical bars. I added the horizontal rings. The rings strengthen the vertical bars which are very fragile without the rings. They also aid in keeping the bars stable during printing.
Gcode is for Ender 3, at 70% wide/deep and 50% high this is minimum recommended size and may need the top trimmed to pass a D20. This is the one in the first picture. Second shows time to print that gcode. This prints the top and main tower in one.
It will print smaller but, good luck finding the smaller dice.
Be sure to Z hop during retraction at any scale or the vertical bars will wiggle making them weak and ugly.
Pictures show upright some places, inverted others. I am not sure what is going on with them.
Cubic infill used.
RETRACTION AND Z HOP ON RETRACTION REQUIRED
Edited in 3D Builder. I added the rings to support the verticals of the cage and the ring with supports to prevent the dice from jumping out.