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Hot white dwarfs (WDs) represent the beginning of the end of the vast majority of stars. They are key objects to reconstruct the various evolutionary pathways of sun-like stars and serve as powerful tools to address a multitude of (astro-)physical questions. However comma the physics operating in the hottest (Teff>50kK) WDs remains poorly to hardly understood comma since several investigations on these short-lived stars rely on low-number statistics. Progress can only be made with further high-resolution FUV spectra uniquely allowing reliable Teff and metal abundances determinations. Gaia and extensive spectroscopic follow-up has now allowed us for the first time to assemble an all-sky sample of the brightest and hottest WDs comma suitable for follow-up with the HST. The proposed Treasury program will triple the number of high-resolution FUV spectra of WDs in the enormous Teff interval 50-200kK and be precious to a broad scientific community. Key science cases aredoublePoint (1) Map metal abundance patterns along the early WD cooling sequence to decrypt several phenomena occurring during that stage (2) Provide powerful observational constraints to test theoretical diffusion comma planet accretion comma and wind models comma as well as stellar evolutionary calculations (3) Assess systematic errors on Teff introduced by optical spectral analysis only comma and by that calibrate our stellar atmosphere and binary light curve models that will be applied to thousands of hot WD from upcoming surveys (4) Identify (hitherto undetected) trans-iron elements to uncover opacity sources and to derive atomic data comma which will allow to investigate heavy elements in hot stars in general