  The discovery of the non-Hermitian skin effect (NHSE) has revolutionized our
understanding of wave propagation in non-Hermitian systems, highlighting
unexpected localization effects beyond conventional theories. Here, we discover
that NHSE, accompanied by multi-type spectral phases, can be induced by
manipulating nonconservative couplings. By characterizing the spectrum through
the windings of the energy bands, we demonstrate that band structures with
identical, opposite, and even twisted windings can be achieved. These
inequivalent types of spectra originate from the multi-channel interference
resulting from the interplay between conservative and nonconservative
couplings. Associated with the multi-type spectra, unipolar and bipolar NHSE
with different eigenmode localizations can be observed. Additionally, our
findings link the nonreciprocal transmission properties of the system to
multiple spectral phases, indicating a connection with the skin modes. This
work paves new pathways for investigating non-Hermitian topological effects and
manipulating nonreciprocal energy flow.
