Start off by cutting a flat slab of foam with a sharp hobby knife. Shape the edges so that they are no longer square, but many faceted. Once you are satisfied with the basic shape, begin carving strange runes and symbols into the foam.

Make a suitable base for your monolith out of whatever material you have at hand. We chose to attach the monolith at a tilting angle so that it appears sunken and ancient.

Paint the monolith any colour you wish. A bright blue was chosen because it'll show up really nice and feature prominently on any gaming table. The runes will drybrush really nicely and stand out with little to no effort. Also some of the exposed interior of the monolith was painted a luminous green to hint at the hidden power within!