While the role of asymmetric nitride clusters on the cage size and symmetry in fullerene-based structures is already well-known, the role of the asymmetric arrangement of metals in nitride clusters on the nitrogen is studied in detail in this work. It is discovered that asymmetric mixed-metal nitride clusters give sufficiently narrow N-14 NMR signals to make NMR the method of choice to characterize the endohedral cluster from the inside. In the series of mixed-metal nitride clusterfullerenes LuxSc3-xN@C-80 and LuxY3-xN@C-80 (x = 0-3) the delta(N-14) values are found to be linear functions of x showing that N-14 chemical shifts are additive values with specific increment for each kind of metal atoms. Density functional theory calculations are performed to interpret the experimentally measured spectra. To reveal the main factors affecting N-14 chemical shifts in nitride clusterfullerenes, shielding tensor components are analyzed in terms of Ramsey theory both in localized and canonical molecular orbitals. N-14 chemical shifts in M3N@C-80 and related systems are shown to be determined solely by nitrogen-localized orbitals and in particular by the p(x,y,z) atomic orbitals of nitrogen. As a result, the peculiarities of the nitrogen shielding in nitride clusterfullerenes can be interpreted by the simple analysis of the nitrogen-projected density of states and its variation in different chemical environments.