A Luminous Rock is a rock native to Altago. It gives off a bright glow that can light up dark passages. It can be bought for 5000 gold from a merchant or Zanibar Ferm, the company the merchant works for. Tia will also give you one if you see her before you set off for Segram Village. It is also the only Equipped item that you can get more than one of, since if you buy one or Tia gives you one, you can still buy another, which means you could potencially have several, if you have enouth money to buy lots.