ΔE 16.1, loose: different enough that you should pick on purpose. Tarnished Brass is a little darker, much more saturated, warmer than Runelord Brass.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Tarnished Brass is a little darker, much more saturated, warmer than Runelord Brass.
The same difference applies the other way round: Runelord Brass is a little lighter, much more muted, 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 Runelord Brass on the colour wheel See Tarnished Brass on the colour wheel
All matches: Runelord Brass equivalents · Tarnished Brass equivalents