Arctic Mirus are aggressive creatures (except on "peaceful" worlds) that will spawn on Peakstone in Mountains and nowadays also on Snow on frozen Oceans, in Taigas, snowy Tundras and Frozen Deserts. Arctic Mirus can only spawn in darkness, and they cannot stand sunlight - just like all night creatures, they will burn away in blue flames when sunlight hits them. Arctic Miru Eyes are needed as crafting-ingredients for Diamond Swords and Fire Resistance Potions (as of R26 in December 2015). You cannot use these eyes in recipes as an alternative for ordinary fiery orange Miru Eyes nor vice versa.