Technology in the Cosmic Era can become corrupted and infested. When this happens to a mecha, the result in codenamed a Hekatonkheire.
The Suit of Purity appears to be one designed for the heroic, but it masks it’s true villanous nature. Anyone who wears it for long is bound to be slowly twisted to the Dark Side.
In seeking to escape serving the Lord of Ravens many a hope flickered and died, for those who oppose him end up serving him after all.
A fine suit of armour that provides protection, but from what?
A certain type of demon cannot not be hit by ranged weapons or attacks. Attacks have to be made up close and personal for the damage to mean something. Ranged attacks are to impersonal.
Possibally a way to make the ranged attacks more meaningful would be to coat the arrow head or what not with the shooters blood. Of course, they'd better be a good shot, otherwise they're wasting arrows and already bleeding to boot.
Spells: wizards might have half or no effect, preist might work due to divine intention.