In later missions you may encounter Dual Horns called Diceratops or Grand Horn. The Diceratops has Null Magic, so you must use physical attacks, but the Grand Horn is very difficult. It has Null Magic and Null Physical, requiring you to wait for the DMW to get you a combination. It is recommended you buy Zantetsuken Materia and level it up to the maximum. Also, buy a Lucky Stars Materia, as the Grand Horn has an attack called Gaia's Wrath which will lower your limit level. You cannot control this one at all, so be patience. You can steal a Pearl Necklace (rare steal) from it.