Conjure Elemental Dragons

You conjure three intangible spirits that look like dragon heads from the Elemental Planes that appear from your back. there are three colours, which determines its damage type: yellow (Lightning), red (Fire), and blue (Cold), Using a magic action you can manipulate these heads, making up to three attacks on any creatures in range and sight, The creature attacked must roll a DC 15 dex save, on failure the creature takes 12D8 damage of the respective head On Success the creature only takes half. The spirits lasts for the duration.