Armor of immolation is a harmful (though occasionally useful) type of runic armor. Each time you are hit whilst wearing the armor, there is a 10% chance that flames will burst out of the armor as if you had opened a Potion of Incineration.
The effect does not trigger when hit by spells, but it can activate if the wearer is shot with an arrow, as arrows are treated much like melee attacks.
Armor of immolation is generally harmful to the wearer, but if you do find yourself wearing it, drinking a Potion of Fire Immunity will protect you from the effects while setting melee attackers on fire. However, the armor's use is limited both by its unreliable 10% trigger chance and the need for Potions of Fire Immunity to make it safe to use. It will also have a lower armor value that normal due to being generated with a negative enchantment.
Creatures immune to fire like a flamedancer, salamander or a will-o-the-wisp are understandably not harmed by the runic effect of this armor.