WE PROPOSE TO OBSERVE THE SIX MOST MASSIVE (3XL014M) CLUSTERS AT Z>1.2 DISCOVERED VIA THE SUNYAEVZEL'DOVICH (SZ) EFFECT BY THE SOUTH POLE TELESCOPE (SPT). THE PROPOSED 700 KS PROGRAM WILL PROVIDE DEEP X-RAY SPECTROSCOPY FOR A SAMPLE THAT IS ALREADY RICH IN MULTI-WAVELENGTH DATA FROM A VARIETY OF TELESCOPES INCLUDING SPITZER HUBBLE AND CHANDRA. THESE NEW DATA COUPLED WITH SPATIALLY-RESOLVED X-RAY IMAGING FROM CHANDRA WILL PROVIDE THE FIRST CONSTRAINTS ON THE THERMODYNAMIC PROFILES FOR A COMPLETE SAMPLE OF GALAXY CLUSTERS AT Z>1.2 ALLOWING US TO STUDY A VARIETY OF PHYSICAL PROCESSES IN CLUSTERS CORES AND OUTSKIRTS AND TEST PREDICTIONS OF SELF SIMILARITY AND AGN FEEDBACK MODELS AT A TIME SHORTLY AFTER THESE SYSTEMS FORMED.