ΔE 23.8, loose: different enough that you should pick on purpose. Undead Dragon is noticeably lighter, more muted, warmer than Pylar Glacier.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Undead Dragon is noticeably lighter, more muted, warmer than Pylar Glacier.
The same difference applies the other way round: Pylar Glacier is noticeably darker, 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 Pylar Glacier on the colour wheel See Undead Dragon on the colour wheel
All matches: Pylar Glacier equivalents · Undead Dragon equivalents