ΔE 62.3, loose: different enough that you should pick on purpose. Nihilakh Oxide is noticeably lighter, much more saturated than Matt Black Primer.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 62). Nihilakh Oxide is noticeably lighter, much more saturated than Matt Black Primer.
The same difference applies the other way round: Matt Black Primer is noticeably darker, much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Matt Black Primer on the colour wheel See Nihilakh Oxide on the colour wheel
All matches: Matt Black Primer equivalents · Nihilakh Oxide equivalents