Two-dimensional electron dispersions with peculiar band crossings provide a platform for realizing topological phases of matter. Here we theoretically show that the e g -orbital manifold of honeycomb-layered transition metal compounds accommodates a plethora of peculiar band crossings, such as multiple Dirac point nodes, quadratic band crossings, and line nodes. From the tight-binding analysis, we find that the band topology is systematically changed by the orbital dependent transfer integrals on the honeycomb network of edge-sharing octahedra, which can be modulated by distortions of the octahedra as well as chemical substitutions. The band crossings are gapped out by the spin-orbit coupling, which brings about a variety of topological phases distinguished by the spin Chern numbers. The results provide a comprehensive understanding of the previous studies on various honeycomb compounds. We also propose another candidate materials by ab initio calculations.Two-dimensional materials with layered structure have attracted considerable attention as a good playground for topological states of matter. The representative example is monolayer graphene composed of a purely two-dimensional honeycomb network of carbon atoms [1]. The low-energy excitation in graphene is governed by π electrons in 2p orbitals, whose energy dispersion has linear band crossings with the Dirac point nodes (DPNs) at the Fermi level, called the Dirac cones. Stimulated by the theoretical proposal that the Dirac electron system is potentially changed into a Z 2 topological insulator by the relativistic spin-orbit coupling (SOC) [2, 3], graphene and similar honeycomb-monolayer forms of Si and Ge have been studied [4,5]. In addition, few-layer graphene has also received attention as the low-energy spectrum takes a peculiar form depending on the stacking manner. For instance, in a bilayer system with the so-called AB stacking, the DPNs turn into quadratic band crossings (QBCs). As the QBCs possess an instability toward a quantum anomalous (spin) Hall state [6, 7], the effect of electron correlations has been intensively studied in bilayer graphene [8][9][10][11].Recently, transition metal (TM) compounds with similar honeycomb-layered structure have gained great interest from the peculiar band topology in their d-orbital manifolds. For instance, the DPNs, QBCs, and topological phases were found in the systems with corner-sharing network of the octahedral ligands, e.g., [111] layers of the perovskite structure [12][13][14][15][16], and with edge-sharing octahedra, e.g., trichalcogenides [17], trihalides [18][19][20][21], corundum [22,23], and rhombohedral materials [24][25][26]. Interestingly, the number and position of the DPNs as well as the shape of the Dirac dispersions strongly depend on the materials. This suggests the controllability of the band crossings and topological phases by using the dorbital degrees of freedom, but such an interesting possibility has not been investigated systematically.In this Rapid Communication, we theoretically show t...