ΔE 23.3, loose: different enough that you should pick on purpose. Bloodfest Crimson is a little darker, much more muted, warmer than Warlock Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Bloodfest Crimson is a little darker, much more muted, warmer than Warlock Purple.
The same difference applies the other way round: Warlock Purple is a little lighter, much more saturated, cooler.
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 Warlock Purple on the colour wheel See Bloodfest Crimson on the colour wheel
All matches: Warlock Purple equivalents · Bloodfest Crimson equivalents