Create a clipart of a majestic unicorn with a glittering silver horn. The unicorn should be depicted in a watercolor style with realistic details. The background must be plain and contrasted to bring out the beauty and majesty of the creature. The unicorn should be the main focus of the image, commanding attention with its regal presence and graceful form. Ensure that the image captures the essence of the unicorn's mythical nature while remaining true to the realistic style.