SCP Foundation

Okay, so the concept is of 6 rings that all grant a boost in a certain attribute.

I would go with D&D attributes:
-Strength
-Constitution
-Wisdom
-Intelligence
-Charisma
-Dexterity

I am amenable to changing the attributes and the number of rings.

However, if a person wears all 6 rings, then they are possessed by the dude who had the rings commissioned.

The rings were cursed to hold 6 parts of that person's essence. And wearing each ring would increase the desire to get the rest of the rings. Maybe, the person would have a feeling of where each ring would be.

That entity would be almost insane but, after many interview sessions, may be amenable to questioning. His objective would be to destroy the rings but the rings would be all indestructible by non-anomalous means.

Also, how should I make the ring creation origins? An obscenely expensive serpant hand commission with an added curse in the "dick genie" fashion?

I must ask, how should I characterize the entity so that he does not cross the "able" line? Can I make him friendly? Any feedback would be lovely, especially ones that would make this not a "Mary Sue" and prone to immediate decommissioning.

Literal D&D magic items aren't likely to work.

The first anomaly here is that D&D attributes are even meaningful in the real world, and getting past that is going to require a lot of disbelief suspension, adding "cursed magic item", "plot coupon", "a wizard did it", and "big bad" to this is four tropes too far.