The Crystal Bow is based on the Crystal Golem, being made of grey stone and decorated with blue, red, and yellow crystals. The arrows have blue and yellow crystal "feathers" and a pointed red crystal head.
Epic Battle Fantasy 4
Found on the Battle Mountain, specifically in a chest at the top of the Diamond Golem screen, accessible after beating the nine-wave foe rush with foes from Crystal Caverns. A Battery is required to get this far, used to open a door a few screens ago.