Star Ocean: Till The End Of Time

Story related, cannot be missed

The Ring of Disintegration is acquired by visiting the Urssa Lava Caves near the end of Disc 1. When you enter this area for the first time head East, then East again, from here you should go around until you reach a bunny statue. Go around to the back of the statue and examine it to obtain the "Rabbit Ears Key". Once you have that, return to the entrance but this time head West. From there, go North until you reach a door that requires the key you just found, use it. From here, you'll be placed in a foggy cave in which you cannot move the camera manually. Cling to the left wall until you see an opening to the mouth of a house, enter the house. The Bunny inside will offer to make the ring for 1,000, 10,000, or 30,000. You can just buy the ring for 1,000, but if you offer 10,000 he'll give you the ring and "Gutsy Bunny", which allows you to get extra EXP at the cost of making enemies harder to fight. Regardless of what you choose, he'll need you to backtrack to the Airyglyph Aqueducts for a Glowstone. Return to the dragon waiting by Bequerel Mountain path; it'll take you to the entrance of Airyglyph. Enter town and head Southwest to the aqueducts, when you first enter destroy the ice north of the room to obtain the Glowstone. Return back to the bunny to have him make the ring, unlocking the trophy.