High entropy or entropy stabilised ultra-high temperature ceramics (UHTCs) are an emerging class of ceramic in which multiple transition metals typically found in UHTCs are combined into a single-phase crystalline solution. Early research has shown the potential performance of high entropy UHTCs to be greater than their individual components with improved mechanical and chemical properties providing a promising emerging range of materials applicable for extreme environments, such as thermal barrier protection. However, there are gaps in our knowledge of the fundamental relationship between composition, microstructure and performance. In this work, we explore a quinary high entropy carbide (HfTaZrNbTi)C₅ which has shown excellent high temperature mechanical properties and oxidation resistance. The materials are fabricated through solid phase sintering starting from carbon and oxide mixtures using hot pressing or spark plasma sintering. The effect of processing on the thermomechanical properties is analysed and related to the materials structure from the nano- to the micro-levels. In particular, atom-probe tomography is used to analyse atomic distribution and interfacial segregation and how they are impacted by the processing conditions. The results provide essential information needed to understand the relationship between composition, microstructure and properties in entropy stabilised ceramic materials and develop their practical application.