Design a mesmerizing galaxy-themed sword that embodies the vastness of the cosmos. The blade should shimmer with vibrant hues of deep blues and purples, reminiscent of distant nebulas, while the hilt should capture the brilliance of stars. The sword's pommel should incorporate celestial elements such as constellations or swirling galaxies. Infuse the design with a sense of cosmic energy and make it appear both elegant and powerful. Let your creativity soar across the expanse of the universe as y