This will cause your foes to burst into flames when they try to harm you.
The Armour of Fire is a mould introduced in Overlord: Raising Hell. It has the ability to set an enemy who strikes you on fire, causing them fire damage over time.
Note that some creatures will not take fire damage. For example, many of the large enemies and ranged enemies will not suffer fire damage over time as with other enemies.
After you took care of the 'playful' Wraith in his recluse, exit the 'indoor' area, keep left up small bump with a closed rock 'gate'. Destroy the skull altar to the left, then use one of the fire spells on a spiky bomb between the rock. The chain reaction will blow up the rock gate, enter to get first of two moulds in the Golden Abyss.