The outstanding thermomechanical and corrosion resistance performance of electrofused magnesia-chromite aggregates (EMCA) led to their broad application in refractory compositions. However, the highly toxic and water-soluble hexavalent chromium cation (Cr⁺⁶) generated during the application and landfilling of refractories containing this raw material have been driving the replacement of chromium-containing compositions by greener alternatives. In this sense, significant efforts have been done to study nontoxic systems, especially MgAl₂O₄-based. Nevertheless, equivalent performance in applications such as RH degassers was not achieved yet. As a consequence, there is a lack of understanding of the mechanisms that lead to EMCA properties, especially related to their high thermal shock damage resistance. Additionally, electrofused magnesia-chromite aggregate is now considered a compositionally complex ceramic (a classification that embraces high-entropy, medium-entropy, entropy-stabilized and nonstoichiometric ceramics), thus, conventional formulation criteria can hardly account for the microstructure complexity of this raw material. In this work, multiple electron-microscope-based techniques were used to assess EMCA microstructural features. Backscatter electron imaging (BSE) coupled with Energy Dispersive X-ray Spectroscopy (EDS) highlighted that the aggregate comprises a magnesium-oxide matrix containing nodular-like precipitates presenting oxygen, magnesium, chromium, aluminum and iron as the main elements. With the aid of thermodynamic calculation (CALPHAD method), the mineralogical composition of the two distinct regions was identified as a complex spinel-like solid solution (spinel^SS) surrounded by a MgO (periclase) matrix, which was in tune with the X-ray diffraction result. The mean size of the precipitated spinel was 15 ± 2 µm, which is above the critical diameter to induce microcracking due to thermal expansion mismatch in this system. However, such cracking is not randomly distributed and Electron Backscatter Diffraction (EBSD) was used to assess its pattern, unveiling a good fit with the {110} family of crystallographic planes. Therefore, the microcrack orientation pattern in the EMCA – that gives rise to their high flexibility – could be attributed to the Zener-Stroh crack mechanism triggered by the stress generated due to the thermal expansion mismatch between the MgO and the complex spinel. Based on this mechanism and with the aid of thermodynamic calculations (CALPHAD), the concepts of designing compositionally complex ceramics were applied to find eco-friendly EMCA alternatives. From the 154 simulated systems, the four most promising compositions were experimentally produced using a laboratory-scale arc melter and characterized by BSE. Although kinetics aspects still must be addressed, Cr-free EMCA-inspired microstructures were obtained, highlighting that this design approach can be used to support the development of novel raw-material that can better merge performance, cost and eco-friendliness.