We present a rigorous, first principles derivation of the Complex Time Quantum Thermal Geometric (CTQTG) master equation,a unified dynamical law that consistently combines quantum unitary evolution, thermodynamic irreversibility, and Riemannian gravitational geometry within a single holomorphic structure. The derivation relies solely on fundamental axioms: complex-time holomorphy, Kähler geometric consistency, probability conservation, dimensional completeness, and stability. The geometric coupling coefficient is uniquely fixed by the Planck scale,leaving no free parameters beyond an order-one dimensionless constant. We analyze the well-posedness, regularity, uniqueness, and positivity of solutions, construct explicit analytic solutions including plane waves and Gaussian wave packets, and explore their profound physical implications. From the exact solutions, we derive bold, testable predictions that bridge quantum mechanics, general relativity, thermodynamics, and the Standard Model. This equation represents a novel, mathematically consistent, and physically completecandidate for the fundamental master equation of a Theory of Everything.