ΔE 16.7, loose: different enough that you should pick on purpose. Hospitallier Black is noticeably darker, more muted than Basilisk Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Hospitallier Black is noticeably darker, more muted than Basilisk Green.
The same difference applies the other way round: Basilisk Green is noticeably lighter, more saturated.
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 Basilisk Green on the colour wheel See Hospitallier Black on the colour wheel
All matches: Basilisk Green equivalents · Hospitallier Black equivalents