Would this be considered an impurity ring?
Not really, but there’s no reason you can’t choose to wear one to mean that to you.
Purity rings are a sort of virtue signal for people who want to tell everyone how committed they are to chastity. Impurity rings just copycat that idea and invert it, I guess to make fun of it? Not sure I see the point but why not?
I would say this sigil is much, much more than just a signal of your commitment to “impurity”. Asmoday is a very advanced being and far from a one trick pony. Some people don’t work with him for lust at all.
You want to anointed it with your private parts juice with yourself first and/or after sex with a partner if you truly want to get the most from it.
On its own as purchased? I wouldn’t consider it anything except a cool ring with a sigil, unless your purchasing from a practitioner that makes jewelry and/or whom consecrated and dedicated the piece or charged it with that energy.
On its own it’s just metal and jewels, so it will have the natural properties of those items, but in my experience without intent the natural properties don’t even do anything.
For example I have worn a large diamond for many years. Diamonds have many magical applications, but until I started working with it and trying to tap into its energy and essentially told it how I wanted it to help me, it was just an item like a shirt.
I’m sure cotton is good for something magical too, I wear it a lot, but I don’t render any benefits from not knowing what it could do it and having no intent when wearing it.
On the flip side I charge my makeup by color and intentionally wear it to produce benefits in my life with the actions of applying it and it being noticed amplifying the effects of the colors.
But on its own, it’s just face paint and fun and doesn’t do anything except glamour me up some.