a black robe engraved with purple gems

[Rialon]

You utter a prayer to your deity.
A warm wave of magic flows through your hands as you perceive that..
.. this object, a black robe engraved with purple gems, is armor,
   and can be referred to as 'black robe gem'.
It is of 19th level, weighs 5 pounds, and is worth 127 gold.
You can wear it around your body.
It is fireproof and resists corrosion.
Only true wizards can use it.Armor class bonus: 12 vs pierce, 12 vs bash, 12 vs slash, and 12 vs magic.
When worn, it
   modifies fortitude save by 2
   modifies mana by 100

What is a true wizard? I can wear it being a priest.

[Proph]

I know this is aside from the point of your post, but the name of "a black robe engraved with purple gems" doesn't make very much sense as far as grammar and word usage goes. To engrave something is to carve or etch into it. This sounds more like it should be "a black robe studded/lined with purple gems".

[Quino]

True wizards I think are supposed to be mages...

To engrave something is to carve or etch into it. This sounds more like it should be "a black robe studded/lined with purple gems".

Hmm maybe embroidered will be closer?

[Habbakuk]

Fixed.