A comprehensive and cohesive abstract tattoo design that covers most of a realistic forearm in natural skin tone, featuring a cosmic time theme. The tattoo should be designed with bold, thick black and grey elements that create a harmonious and unified composition. Incorporate large concentric circles and spirals that extend across the forearm, seamlessly integrating geometric patterns such as triangles, hexagons, and stars. Ensure that these elements blend smoothly into each other, covering a substantial area of the forearm. The design should include an abstract sun and moon, with fluid shading that enhances the overall integration. Aim for a clean, sophisticated look where the black and grey ink forms a striking contrast against the natural skin tone, with the tattoo providing full coverage and creating a striking visual impact."