Generate a breathtaking image depicting a colossal battle between mythical creatures and futuristic war machines amidst a post-apocalyptic cityscape. The sky is filled with swirling storm clouds crackling with lightning, casting an eerie glow upon the chaotic battlefield. The ground is littered with debris and flames, while towering skyscrapers crumble in the background. Showcase a dragon-like creature, with scales shimmering in shades of obsidian, unleashing torrents of scorching fire upon towering robotic mechs armed with advanced weaponry. Surround them with a diverse array of fantastical creatures, each engaged in fierce combat, ranging from agile winged warriors to hulking behemoths. The scene should exude a sense of grandeur, devastation, and raw power, as if the fate of the world hangs in the balance.