What is this, and how do I get one?

Ark Ring as in the 9th Anniversary Ring? I never really pay attention to names of items.

If that's what you're referring to....because you need something like 9 other pieces of equipment to obtain the full effects, which means if you have any other set you're pretty much not going to bother. I only got the ring because it had Potential and there's not many special rings released in JMS.

No no, like the High lords oracle ring or what ever. The ones you need to beat Arkarium for the Recipes for.

Immortal Hero Set (#52)
2 Set Effect

All Stats: +15
Weapon Attack: 10

http://maplearchive.com/item.php?id=1112664