Using high-throughput calculations we have investigated the effect of interstitial B, C and N atoms on the stabilty, structural and magnetic properties of about 250 magnetic compounds with cubic symmetry. Permanent magnets requires in addition to a large saturation magnetization and a high Curie temperature a large uniaxial magnetocrystalline anisotropy energy. For cubic magnetic compounds, often the first two requirements can be fulfilled, while the magnetocrystalline anisotropy energy is typically small due to symmetry reasons. We have shown that in several of these compounds interstitials can lead to a stable, distorted structure with large magnetocrystalline anisotropy energy, in some cases comparable to known hard magnetic materials like L₁₀-CoPt. Further, we have calculated several binary Fe and Co phase diagrams in the pressure range between 0 and 15 GPa in order to find new magnetic compounds which can be stabilized in high pressure synthesis. For Ca-Co and Bi-Co, where no stable ambient pressure phases are known, our calculations predict CaCo₂ and Bi₃Co to be stable around 5 GPa, in agreement with their recent synthesis at high pressure [3, 4]. In addition we predict several so far unreported phases to be stable in high  pressure synthesis. Our HTE database was also used to analyze the effect of substitutional elements on the stability and magnetic properties of YFe₁₂ (Fig. 3). RFe₁₂ compounds can combine a high Fe content (92 at.% compared to 82 at.% for Nd₂Fe₁₄B) with energy products similar to Nd₂Fe₁₄B [5]. Up to now there is however no stable RFe₁₂ phase reported and the ThMn₁₂ structure has to be stabilized by substitutional elements. In agreement with experimental reports, Ti, V, Cr, Al, Si and Re are identified as stabilizing elements for YFe₁₂. In addition, we predict new stabilizing elements, where in contrast to the so far known stabilizing elements a degradation of the magnetization can be avoided.