Pyramid by Kreis Magic

The magician places a card case on the table. The case contains a deck, which serves as the prediction. A spectator is asked to select a card from another deck. The selection is the eight of diamonds. The magician picks up the case, and takes the deck out of it. The cards are linked together somehow. Being unfolded, they form a shape of a diamond, consists of eight of triangles. That means, the prediction is the eight of diamonds. Upon the cards are split, the eight-diamond card appears.

Comes complete with gimmicked deck and instruction manual.