The Astral Plane Gateway is a surreal, monolithic structure with a brutalist design, featuring sharp, angular edges and a massive, imposing frame. Its surface is a mix of smooth, polished stone and rough, weathered textures, with intricate, glowing runes carved into its surface that pulse with an otherworldly light. The gateway's center is a swirling vortex of vibrant, luminous energy, contrasting with the dark, muted tones of the surrounding structure.