Lanthanide-based single-ion magnets (Ln-SIMs) have garnered significant interest for their potential application in molecular-level information storage devices. Among various strategies to enhance the magnetization blocking barrier in SIMs, synthesizing highly axially symmetric compounds is the most promising approach. In the present work, using state-of-the-art computational tools, we have thoroughly examined the electronic structure, bonding, and magnetic anisotropy of lanthanide mononitrides