The dragonstone ring (i) is an upgraded version of the regular dragonstone ring. It can be imbued as a reward from Mobilising Armiesminigame. The player must provide the dragonstone ring to one of the officers in the Officers' Tower (Player must have 200+ rank). The cost of doing so is 141,300 reward credit and a normal dragonstone ring.
Even if you have an onyx ring (i), there are occasions where the imbued dragonstone ring is recommended as despite having lower stats, it costs less. Choosing this ring allows you to take another expensive piece of equipment, without risking it.